If you have 2 stop, e.g. Ewr-ord where you stop for more than 24 hours, and ord-phl where you stop for more than 24 hours, and finally phl-ewr, is a normal allowed route from *A.I didn't know that someone charges more miles for it.
That would be 35K on CO.CO allows free stopovers on all free tickets except the domestic 25K ticket, where there is a 10K premium.I have had success with stopovers on other tickets like within Hawaii (3 legs with stopover for 10K) and flights to Hawaii (40K with stopover) for example without paying a premium.I don't think UA ever allows free stopovers within a single region.