When we hear old recordings, there’s a good bit of extra noise that gives the track a vintage feel. There are plenty of ways to add more effects and color after recording, but it’s a lot more difficult to remove them after the fact. In that sense, recording is similar to cooking in that you can always add more later, but you can’t (easily) take it out. Do yourself a favor and keep your original tracks clean and flat. You’ll have a lot more artistic leeway when it comes to mixing time.
You can read more on the subject here: http://audioundone.com/clean-and-flat