Yeah, if it goes into the largest gear without binding or ripping the derailleur off then it is fine. Your largest gear will never get any larger so if it works then it works.

But remember this discussion if you change your cassette in the future - if you have a 28 tooth big cog now and switch to a cassette with a 32 tooth big cog and you don't replace the chain, you may wind up walking home with a bunch of derailleur parts jangling in your pocket.