The advice I give relies a lot on how long you plan to live in the home. My last 3 homes averaged 12 years before moving. Therefore, I like to do all my major updates in the first 5 years of ownership, then just do smaller updates and maintenance on going as needed or wanted.
This is what we did with our current home. Massive updates years 1-4 and now we just maintain and do little projects to keep it fresh looking, to code  and operational.

I would say it is based more on need first. 

Second to that may be the desire combined with affordability. 

It should be based only on need. Don't let anyone fool you with bogus update timeframes. They are designed to take your money. It's just marketing. Unless you need the new dark countertops and backsplashes to the ceiling, but beware, next year the hottest new trend will be something different and if you NEED to keep up with the trends, then you will need a new kitchen frequently because they said so. 

Peter Mohylsky, 

I have been begging for upgrades for years, it is based on want, lol

It depends on their Financial Ability and can we get a ROI  ………. 

I did many upgrades after I bought before I moved in.   Since, have done kitchen countertops, changed out countertops in two bathrooms, mirrors, and lights, sinks & faucets.   Still need to finish the master bathroom with tile, stand along tub and new surround.

In the world of sales, only when necessary is the rule. On owning & having money & desire, go for it. No place like home (the way you want it)

When discussing this with sellers it depends on cost, ROI, time to complete, condition of the house and several other features.  If a seller wants to put in new flooring, but leaves the 60 year old kitchen alone, then I advise against it as the flooring will be a wasted expense since it'll have to go if/when the footprint of the kitchen changes.

We recommend upgrades when selling because upgraded houses sell quicker, for more and provide good ROI to the seller.

I don't think there's any schedule. It depends on how dated a home is and how well it's been maintained. 

Does it still function?

 Are you planning to sell?

 Do you just "want" an update / upgrade to the latest and greatest?

 Are you going to completely rip out the existing kitchen?  If yes, do you have a bonus room that will function as a temporary kitchen?

  Are you aware that modern appliances have been severely affected by Government regulations?    And that some locales restrict or prohibit such things as new gas appliances?   For example, the many complaints that new dishwashers don't get the dishes clean?   Be careful!   They will try to wow you with "Energy Star" and "Green Certified" designations... those are fancy ways of saying, "It will not perform the way you want it to perform."

    And, as Matthew Sturkie, CRS, GRI 909-969-3805 said in his reply on this page, "It's just marketing".   The paint companies, the appliance makers, the countertop manufacturers, interior designers, the big box hardware stores, et al have a vested interest in convincing you that you need to buy and install their products.  Their marketing includes promo pieces and advertorials on "News Channels" like Fox and Daily Mail.   

    If you plan to gut it and remake it, I suggest you visit some model homes in the new subdivisions in your area, preferably on the higher end.   See what is going on, what is available.  Take your time!

It really depends on the home and the seller.  The level of need, and the ability to get things done.

Kathleen Daniels, Probate & Trust Specialist and I are on the same page, so I am moving on. 

Trends seem to change every 7-10 years. Updates all depend on the quality you started with, the owners need and what the market is showing if it is for a sale.

I don't often recommend an complete update to sell unless it is pertinent  I do recommend various things to get the house sold such as painting, replacing flooring, new countertops, etc. I look at the market and what the trend has been for the neighborhood.

Also, doing a full gut job is usually an investor and for a flip not usually a resale. In my own home, I did a mini kitchen & bath update around year 12 and then updated my kitchen and 1st floor flooring at year 20. 

I update when I buy a home (over the first 1-2 years) so we can enjoy the updates while we're living in the home.

Since we move every 6 or so years, we rarely need to update again! LOL 

With all of the renovating I've done (including investors' sales), I have first-hand knowledge of the best appliances, best places to find lighting, etc. As well, I know who does the best work in the business (trades)!

For now we are just maintaining.  If you plan to sell it might be time to update kitchens, baths and paint.

People seem to like the retro look. One time I was showing a home and walked into the kitchen. It reminded me of a kitchen in the 1950s I was so excited I thought "man I wouldn't change a thing!"...lol

     Not looking for trendy but classic, solid, functional. Got a heck of a deal on labor over the winter months a couple years back so went stem to stern one of the lake homes. Did same in other the before that because has super carpenter wanting inside work.

     When dollar was 40% higher than loonie value, got a brand new hickory kitchen & pantry custom cabinet set for intown home made in Canada, 12 miles into New Brunswick.

     Have a farm property rental with state trooper in it now. Always adding something to the 7 buildings at the farm.

I would suggest painting the outside once every seven years.  The front and backyard shoue be maintained right along.  The insice should be kept in good cosmetic condition.  That's it.

A former teacher of my husband's, who is still a good friend, is 102 years old and still manages on his own! His house is a "living museum" of the 1950's. That I would say needs an upgrade! Actually, whoever buys that property, eventually, will probably either gut the house or raze it and start fresh. Other than that, it's the proverbial "depends".