Macbook air wouldn't turn on until after I reset the SMC. Does this indicate any further problems? I put my macbook air to sleep this afternoon by closing its lid, as I usually do. When I got home a few hours later it wouldn't turn on and didn't respond to the power button being hit. 

I followed the instructions on Apple's website and reset the SMC, after which it turned on. It's now working fine but I'm wondering if this problem indicates any problems with my air or if this is something that just occasionally happens. FWIW, this has never happened in the ~2 years I've owned the device. 

If this is indicative of possible future problems that may render my air not usable then I would like to know now so that I can get it preventively serviced.
Resetting the SMC usually solves power-related problems (fan handling, sleep mode, etc).

The procedure is quite simple and documented, meaning that such problems are quite common and usually do not indicate the existence of anything worth worrying about.

Actually, it is advisable to reset the SMC and PRAM (start up with Command, Option, P, R pressed) periodically; also, while you're at it, you might want to repair disk permissions (using Disk Utility in the Utilities folder) and verify the Hard Disk as well.

If you keep your Mac well maintained, it will remain healthy for a long time: my MacBook Pro is 4 1/2 years old and still rocking thanks to an SSD upgrade ;)