Since you're asking for opinions....
Yamaha recommends 3000 mile oil changes and 6000 mile filter changes.
I personally think it's insane to change the oil but leave the "dirty" filter in the bike for another 3000 miles.
The bike doesn't take very much oil, and the filter is laughably small.
So for me, an X rider that spends 95% of the time riding on the street, I like the piece of mind I get from from paying a bit more for special motorcycle oil and not worrying about the exact miles I've gone between changes. If I change oil at 2500 miles, or for whatever reason let it go to 3500 miles I don't really lose sleep over such things. Since I change the filter every time I change the oil, and I use some fairly expensive Amsoil synthetic I rest easy at night.
If I put cheaper oil in bike I'd be much more concerned about those kinds of details.
I like synthetic, designed for motorcycle, oils so I don't have to be nit-picky of such things.
I've got over 10,000 miles on my bike and it runs like a well-tuned top.
Bottom line is this - Yamaha built these bikes to be pretty much bullet proof. Do what-ever helps you sleep well at night. Other than outright neglect chances are good you won't be hurting the bike.
_________________
2008 WR250X
Gearing: 13t - 48t
Power Commander 5 / PC-V
Airbox Door Removed - Flapper glued - AIS removed
FmF Q4
Bridgestone Battlax BT-003rs