you'll see roots coming out of the drainage holes when it becomes rootbound. do not overwater but keep moist when you transplant and it'll slide out of the old pot much easier while leaving the root ball in tact. have your new pot ready to receive the plant before doing anything by adding a little super-thrive to the hole (or any stress reducing hormone product from your local nursery) and a little more around the plant after it goes into the new pot. then let it be for a few days...it aready has plenty of water and nutes and rest is needed while it grows into its new environment.

glad to see ya lost the foil too...aluminum foil is beyond worthless in a garden. flat white paint or mylar is the way to go...