I clean my bobbin area pretty much every time I sit down at the machine. I don't use terribly low lint thread though either, just inexpensive thread from Jo Anns and Connecting Threads. If you are getting nests of thread on the underside of your fabric or your thread is jamming up on you while you sew, it's often because you have lint in your bobbin area. When I was new to sewing I didn't know this, and I even gave away my great grandmother's sewing machine because I thought it was broken! Oh how I wish I had kept it!!! :(
As for oiling, you are supposed to do it more often but I oil just a few times a year. I don't sew everyday though like many of the ladies here do. Many computerized sewing machines don't need oiling at all and even recommend against them, so as others have suggested, check through your manual. ;)
I change my needle every new project or so...if I just made something small I don't bother. If your needle breaks, your thread starts breaking, or you begin skipping stitches, then your needle change is over due. ;) If you have changed your needle and you are still having issues, you might need a different needle size. Anything beyond that and I'd go running to the manual myself so I'm not very helpful! LOL*