i did the reverse, ran out of sust switched to test e, no issues. i frontloaded a bit to let the long ester do it's work while the sust active lives ran out, but i think you will be fine without a frontload since you're already running a long ester.
to be honest i kinda preferred the sust, had more of a "kick" to it. i'd say 3x a week and preferably on workout days to take advantage of the prop in the mix.