There is a maximum of 186 minions which can exist at the same time (at least in practice mod/ while approaching the limit only 2 minions spawn for each lane and after the limit zero minions spawn). (btw. it was satisfying to kill enemy minions near any ally dummy with Galio´s ult)
Flashing from one base to another (starting and ending in the middle of the fountain) requires 50 flashes.
Or you could use 4 Galio ults to travel from one base to another. (fully skilled abilities btw.)
You can also get from one base to another with 3 Taliyah ults.
Another way to travel from base to base is using 11 times Zac´s E.