If you have oil for the next several changes, avoid buying unless the oil is dirt cheap.
I consider dirt cheap qt for syn or qt for anything else.
Invent your own purchasing rules.
You can sometimes find oil really cheap.
Even observing the dirt cheap rule, you can build an impressive stash of quality motor oil, and you then have no problem doing someone the favor of changing their oil, in return for which they offer you the use their pickup (working truck, not toy) for a day of hauling, or they have no problem lending you tools or garden equipment.
There may be a universal closeout of SM when SN becomes the current API standard, for example.
By early next year, SM may be marked down to almost nothing everywhere.
That's when you'd load up.