Hi just tried this. Based on example of 1% every 3hrs it seemed like a nice curiosity that wouldn't change the game significantly.

But on vulcanus all foundries get relatively quickly upgraded thanks to their high crafting speed which I didn't expect and wasn't clear from description.

Just wanted something small that would give a few quality buildings without being a significant mechanic. Don't think I'll use this mod again. And that's OK maybe it wasn't for me.

Wish the description was clearer on this! Or if there was a setting so the upgrade credits don't increase as much with crafting speeds.

Hi! Thanks for the feedback!

Sorry about the documentation, it's hard to describe all the nuances up front and clearly.

I'll look at adding the setting to manage whether crafting speed helps or not. I think it's doable!

By the way, there is a quality mod that I think only uses time as the metric for upgrading. I haven't played with it very much, but may be worth a look if you haven't checked it out: https://mods.factorio.com/mod/upgradeable-quality

There is now a setting to enable or disable the crafting speed bonus! It's in startup settings, under the 'Manufacturing Hours for Change'

The mod was updated for factorio 2.1, so you won't get the update until after upgrading factorio.

... and now I'm realizing I didn't give you a shoutout in the changelog. I'll update that. Also, thank you for the suggestion!

Some other things that may impact your gameplay experience:
- turrets provide upgrade credits for other entities, and I suspect you wouldn't want that - railguns on space platforms can create a lot of 'upgrade credits' that get applied to secondary entities like inserters. This should also be pretty straightforward to add a toggle for, I'll look at doing this soon.
- late game progression for secondary entities tends to be pretty high when you have a ton of assemblers generating upgrade credits, even with the new setting it might be too quick. I haven't play tested, so I'm not sure though. Either way, I'll look at improving this so it feels more consistent.

Right, Foundries have base crafting speed 4 and crafting speed 10 at legendary. https://wiki.factorio.com/Foundry
I was using Quality++ mod for additional tiers which are extremely hard to reach but Foundries just auto upgraded to near highest tiers effortlessly, making Quality Control the best mechanic for getting these. https://mods.factorio.com/mod/Quality-Plus-Plus

That makes sense. The new feature to turn off speed was a really good idea. I've been trying out the new mode with crafting speed bonus disabled and it's a lot more intuitive.

I'm tempted to make it the default for new installs. Thank you for suggesting it!