If youre running a hydrogenation you have one chance to charge your Pd/C (at the beginning), and if it dies before the hydrogenation is complete you’re going to have to stop the reaction, filter and concentrate and run it again to from step 1 to achieve complete conversion. You can’t just open the vessel and charge more Pd/C, palladium isn’t forgiving like that. And 1-3wt% is still considerable on a multiple kilogram scale using precious metal…
So while you obviously want to use less catalyst than more based on cost, you definitely want to use enough that your confident that the reaction will be complete otherwise your product is inferior to someone who DID run it to completion - not to mention you use way more time/catalyst re-running the reaction in order to complete the conversions of all THCs to HHCs. Rerunning a half complete reaction still requires the same catalyst loading. Using less catalyst isn’t really a measure of safety at all, it’s directly tied to process cost and reaction time/completion.
Edit: with this in mind, trying to re-use hydrogenation catalyst without ensuring it’s still active is not a smart move. Say it’s only 50% active after the first reaction? You’d never know from just looking at it. Then what? You run a hydrogenation with it that doesn’t go to completion and then you waste a ton of time having the run the material again.