I had built a new computer last may or so, and got all my rebates, finally.  Got the last one a week before christmas.  Been so long I had forgotten about it and it was for a case I had bought.  And yeah a lot of paperwork and number writing.  
So next time I build a computer, I dont think I will include the rebate price reduction in my figures, as it may take 6-8 months for some of the rebates to clear.  And by gollies  

  with my memory if a company waits long enough and they "forget" to send rebates, I'm SOL.