I would only use the 0.5mm needles every 2 weeks to help the tropical products penetrate your skin deeper.

If using 1.5mm needles,then do needling no less than 8 weeks apart.Some ppl do it less than 8 weeks,I prefer to do it every 8 weeks or more.

Collagen is very fragile,it can also take upto 6 months to renew.I believe,too much treatment in a short period of time can it damages the renewal of the collagen.I also believe,longer inbetween needling is better for improvement.