As WheelieNick says above, you can't be sure.
You question is in two parts I think. Your first concern is for how long will Apple support it into the future with updates and upgrades. The second is how long will it function.
Apple generally supports existing Macs for about seven years, give or take, so you might get a few more upgrades with your Air before it reaches its ceiling. It should be usable for a few years beyond that.
As to how long it will keep going is an imponderable, but baring hardware failures it could easily be working well into its second decade. Like WheelieNick, I have a 2009 computer (MacBook Pro) which I use as a family content server in the house. We also have some superceded 2011 'Pros, one of which I use as an away from base Mac - my main Mac is an iMac. The MB Pro can't be upgraded beyond macOS 10.13 High Sierra and is now starting to encounter difficulties in the security requirements of some websites and this will only get more pronounced. But for the main part it's perfectly serviceable for minor tasks. It is, however, slow given the very old specs with which it was made and the demands of newer software.
You will have to judge the moment to get a new Mac depending on your budget and the need. If you Air is serving you well now. I suspect you have already answered you own question when you say "there is not really any great benefit to me in an upgrade". But at some point there will be a benefit in a hardware upgrade. That's something you will have to judge for yourself.
Shakespeare knew a thing or two about computer hardware upgrades: If it be now, 'tis not to come; if it be not to come, it will be now; if it be not now, yet it will come.
