Let us start by saying there's no certain and 'one-fits-all' answer to this question. This could be the end of this article, of course, but in reality, there's quite more to say to this: so, keep reading :)
Reasons for a Change
First off, lets name few most common reasons for decor change. Primary one - you just get tired of same old look and want to spice up your room. Your mood, quality of life and overall feel is what matters most - so that's why we do all these things, right? That's quite the main reason for those changes, and you'll be surprised how little it takes to make a drastic, positive change to your home.
Sometimes it takes quite a little effort to change your decor
Decor Change at Relocation
Another reason is just relocation. United States is country that loves to move and quite easily does so, compared to another countries; per census average US citizen moves 11.7 times per life. We are not sure if that statistic fully exists for all other countries but most likely average person around the world moves less.
When moving to another place, doesn't matter if it's rent or purchasing a house, of course it always involves decor and furniture purchase / re-arrangement. Of course, when these movements are not-rare (quite common for person in 20s and 30s) you think about these things less and put less effort to let's say rented apartment. However, everything changes once you get a family and settle in seriously for the first time.
Ways of refreshing decor
While some sources recommend repaint walls every 12-24 months we think it's quite excessive. Repainting walls is quite often the major step of refreshing the room and doing some decor readjustment, however it's not for everyone. Most people are perfectly fine with walls - so in most cases you'd need to reorder (rethink) your furniture, re-arrange your furniture or just consider a few minor extras to make your room more refined and enjoyable.
Repainting the walls of course is nice and major way of completely changing a look. That's not for everyone though - an effort in itself, it will require all furniture relocation to another space, quite a time to do a full repaint. Also, you'd need to carefully consider if your new color would match your old furniture; this can be a trick on its own.
For the most part we'd just recommend of replacing some of your older furniture with newer, more suitable models.
What do I do with old stuff?
Ready for a change but don't know how to get rid of your old furniture? Consider following things:
Another room. You'll be surprised how often older furniture can serve in different room - in most cases you'll breathe second life in your older furniture piece when it's placed in some other place.
Garage. You probably have a garage or another 'service area' in your home that doesn't have to be fancy. Most of older furniture will serve best in those areas.
Sell it. In most cases you'll be able to sell your furniture for a fraction of original cost to people who actually need it. You'll be surprised but most of old furniture even with damages or imperfections will get sold using your local ad groups, like facebook's marketplace or craigslist.
Donate it. A lot of folks out there would appreciate your old furniture as a gift. Churches, low-income neighborhoods, some newly arrived immigrants, etc. In some cases, you can also get your tax benefits by donating your furniture! Just google on how you can properly do it in your local state / area.
How often should I change my decor?
Listen to your gut, no one will tell you how often you should do a thing like that. If your room and furniture serve you well and do everything perfectly to make your life easier and enjoyable - you don't have too! There are no countdowns, dates or some certain guidelines to do a 'refresh'. Everything, however, can become boring + furniture can become quite used over time, so in certain situations you'll have a change pending before you'd even consider it.
For younger people that love changes a 2-3 year time span would probably be the ideal timeframe. Again, you can stick to minor changes with a focus of refreshing your decor.
As a moderate goal - 5 year time frame would probably be in the middle. 5 years is quite enough to get used to anything to the point you'll meet any change with great enjoyment.
As for a long-term change timeframe we'd say 8-10 years is probably the very safest number of years you'd want a change in quite a certainty. After this time, a great probability of stagnant, outdated decor is almost inevitable.
But again, those things can be subjective, and you will only find your own pace with decor changes by yourself.