Spare Parts may actually time gate upgrades FURTHER, depending on conversion rate.
If you don’t know, Spare Parts are new and going to be made in the Workshop, and should reduce upgrade times by about half. Upgrades will now also be instant, and, you can buy Spare Parts with Gold, though they have not said the conversation rate. But, the key distinction is that the actual process of simply pressing upgrade is now time gated by Spare Parts, as they’re now required for the upgrade alongside Silver. Before, you could always have an upgrade going and save your Gold for the later upgrades (which are more efficient). If you have a massive stockpile of Silver you can no longer just upgrade a lot of lower level stuff or use a bit of Gold to rush lots of high level stuff, now that will be time gated by Spare Parts. That said, if the conversion rate isn’t too egregious, then this won’t be an issue. (And this also shouldn’t apply to UE items as they already have instant upgrades.)