It's very quick to freeze & unfreeze a synth. I agree with Bob - try it and see how you get on with it.
A couple of workflows spring to mind.
- Just freeze the foundations of the song - Pad, Bass, Drums etc - anything which will let you "go with the flow" when adding new parts.
- Just have a scratch, repeating drum loop going while you work on the melodic side of things.
- Freeze everything apart from the track you're working on.