Christ, how many stuff do you sample, then? A song shouldn't be made of more than 1 or 2 sampled passages to spice it up, everything else is supposed to be your own arrangement. And it can't be hard to either adjust the project's tempo to the sample or the other way around then.
I mean there's really no official limit to how much you can sample, and i just mean that the drum machine is a real pain in the ass if you want to use any sample in tempo, and due to the fact that you have to put everything into the drum machine sequencer (even stuff that shouldn't use a drum machine interface such as melodies) makes it impossible to work with different tempos, change speed at any point in the song, or do anything outside of the rigidness of the drum interface, which is how it should be for making a beat, but they instead had it be used for everything else too, which makes it a huge pain in the ass.
Anyways, I downloaded Reason, so this thread is now a debate about FL.