I would imagine most people would say in general it's more common to get a good mix and master seperately, but I don't think that means you can't "master as you mix". I do it, and I'm pretty sure other people do as well. But a lot of mixes get sent to a mastering facility, so obviously a master as you mix approach wont work.
But Mega Dave's issue isn't with mastering, it's with his mixes peaking the mixbuss. If all you do is apply a limiter or other mastering type plugins on the buss, it's "band-aiding" the initial issue of peaking the master buss, and isn't necessarily solving the issue, only covering it up...and more than likely hampering the learning process. If the mix is falling apart when those mastering tools aren't there, then the mix is what needs work.
In the OP's scenario, mastering is irrelevant to the problem IMHO, because he never once mentions his intention is to master as he mixes. If he is, then the problem's solutions could be different.