It will affect your results,. but to what degree is uncertain. Probably minimally, though I have heard of a few people taking much larger doses of finasteride and finding they had much better results. If cost is an issue for you, you should be using Proscar or Fincar, as these drugs will cost you a mere $200/$60 a year.
I cut mine to 1/2 but the result is unclear since I started minoxidil at the same time and shed a lot. I have gone back to the full tab until I reach a plateau of results. Dumb of me to try to make to many changes at once and not understand what was causing what.
Here's my opinion on everything when it comes to Finasteride.
If you've ever bought a bottle of propecia, they give you a nice little graph explaining the average hair count of 4 populations who used and didn't use propecia (Finasteride 1mg).
The people who did notices an increase in hair count in the first 6mo-1year and then slowly petered off over the next 5 years. So in my mind I know that if I take 1mg every day, I have a really freaking good chance to end up like that graph. Any other dose, and I just dont know. So that's my plan for the first year: 1mg (or greater) daily. When that's done (or i lose my left testicle) then i'll start messing with stuff.