Age matters less than structure when moving seedlings outside, and the markers are four to six nodes, a stem that does not flop when the pot is tilted and roots that hold the root ball. Younger than that and slugs, wind and rain take a toll, while older plants in small cups arrive rootbound and sulk for a fortnight. Photos of seedlings at two, four and six weeks and how each fared outside are posted on https://kushindicaseeds.com. Three to four weeks from sprout is the sweet spot.