I have finally now finished all the Rx'd eye drops over 6 weeks post cataract surgery. In general, when can I put in OTC drops from time to time?

6 weeks. There's different types of drops. Most are more or less, water. 2 weeks is probably plenty for the risk of the surgical wound being open and increased risk of infection but 6 weeks is generally the rule of thumb for healing being complete.

There is the other issue of if the drops have some active ingredients but OTC eye drops don't have those.