I'm asking because I often have long voice over projects that take about 20-30 hours to record and edit. It's very detailed work that results in hundreds of small audio clips on the timeline. Somewhere during the process I often shift Reason's master tempo by accident. I don't even know how or when it happens, but suddenly on the 3rd or 4th day of recording, when I go back to listen to clips recorded on previous days, they sound phasey, and sure enough somewhere along the way, the tempo was altered by a couple of BPM and Reason stretched the clips accordingly.
The problem is easily solved by selecting the clips and disabling time stretch, but that also slightly alters the position of the audio in each clip, forcing me to re-edit everything. Changing the tempo back to its original setting won't work because that'll throw off more recent clips that were recorded at the new tempo. So either way, more editing work is required

These projects are not tempo-based, so timestretching isn't necessary and tempo doesn't matter. What matters is having everything locked down and not changeable.
I suppose another approach would be locking the tempo. Is there a way to do that? Is it as simple as creating a tempo automation lane with a single automation point that spans the entire project? I guess I should try that...