I contacted the SimpleSync developer about how the app works if you cancel it for a while and reinstate it later (my POS events are seasonal). He said you'd be billed for the full month each time (I assumed that), and that the sync would just work again whenever you re-subscribed to the app.
No setup/settings to be lost if you uninstall the app for a while.
i'm glad that simple sync exists, but i honestly hate that i have to pay more for this. even more, i hate the idea of duplicate items. it just seems like its asking for trouble somewhere down the line.
this feature has been requested for YEARS and shopify won't implement it. worse still, you can only discount a product but there is no way to adjust a price UPWARDS on the fly. ridiculous.