light stress during veg - possible?

Hey all. Im now starting to veg my seedlings on a 18/6 schedule (closet setup - sealed from light) and ive been giving hourly temp checks in the dark period to see if i need to get a heater or something (for now it seems ok though) my question is - am i causing strees to my seedlings? i know some pepole veg for 24hr/day but still i wouldnt want to harm the little guys in any way.

No they're fine. They'll veg happily anywhere between 16 and 24 hours of light daily.

The 18/6 light schedule will help your seedlings show preflowers sooner helping thus to determine sex.

oh cool. when do you think i shouold expect preflowering then, less than 4 weeks?

Around 3 to 6 weeks from seed depending in genetics.