Fully agree with Murray.
When I was flying Cessna's around Athens I was constantly busy either flying (the easy part), responding to overzealous ATC and avoiding the oncomers to the old airport.
Hence, if you imitate reality 100%, even in a smaller plane you must always have your eyes open and your ears on the look out for anything unusual. And believe me, unusual things happened often (minor failures, popped-out breakers, gauges out of calibration etc.)
So really, no time to rest...

By the way: have you tried letting FS have some failures on your plane? This is standard Simulation Training in real life and can really catch you off-guard if you're not careful.
Saying that; some of the procedures we have to execute on IVAO etc. can be much harder than flying the Cessnas!!