hardening things off

OK so I have some (not as many as I'd hoped but that will teach me to overwater things) french beans about 8/10 inches tall & some corn which is about 6 inches tall & I've been putting them outside for the last couple of days under my frosted window "coldframe".  How long should I be doing this for & when can they actually be planted out?  My allotment is right on the coast so fairly mild temperatures but it still seems a bit on the chilly side to me.

OK so I have some (not as many as I'd hoped but that will teach me to overwater things) french beans about 8/10 inches tall

Seems rather tall prior to planting out to me, and as I only grow fine french beans (fillet/whatever) I try not to let them get too vigorous/short & sturdy, but that seems rather tall to me for this time of year.

Another thing is that if warm & windy when you put them (from a sheltered environment) out to harden off, the leaves could get burnt off by the sun/wind, and a taller/weaker plant could be more susceptable to this and more likely to get it's leaves burnt off.

Mine are just as tall and i've been putting them out during the day as well. Bit chilly still here (forecast is for same all this week ) My runner beans are the same
but next warm spell we get i'm gonna plant them out. I have plenty of fleece to hand just in case