So when I was in this "all campaigns on hardest difficulty" race, I would find my game crashing quite often when loading certain saves, so naturally I resorted to Google to find some fix for the issue. What I found is that any version of AoE prior to 1.0c (1.0/1.0a/1.0b) and version 1.0 of RoR work totally fine and do not experience these crashes. Upon further investigation, it seems that loading a save that was saved while any projectile is being fired causes a crash upon loading, but using these game versions will prevent such crashes. You don't get to press period to select idle villagers, but it's a good tradeoff, in my opinion. TL;DR: Instead of downgrading you can always just be careful with your saving habits, but downgrading is just for safety's sake.

One issue if you'll run "all campaigns" or just the First Punic War campaign in particular is that it crashes upon starting the campaign in RoR 1.0, but works fine in 1.0a. (designed for 1.0a somehow?) Therefore you can either keep 1.0a and do all campaigns with careful saving (or no saving if you're good), or just save it for last with 1.0 and quickly exit out of the game and patch it, or just have a separate folder for 1.0a for quick switching so you can avoid patching mid-run.

The link for AoE 1.0b (latest version without the glitch) will be in the "Resources" section on the left panel. I think that a fresh install of RoR from any disc will produce version 1.0, including the Gold Edition disc (can check version by going into multiplayer and creating a game room), but in case there's someone with 1.0a on the disc, there will be a "downgrade" in the resources section on the left.