Retargeting a high-ticket service like roofing or dental implants makes the window question tricky. Most people default to 30 days because it's the standard option, but a 6,000 dollar job can take two months to close. A 30-day window mostly catches people who already called or ghosted, while the ones still researching drop out of the audience and see nothing.
I'd split it. Keep a short 7 to 14 day window for people who hit the pricing or booking page, since they're close to deciding. Then run a 90 to 180 day audience for anyone who only read a service page, with a different message, like a guide or a before-and-after, instead of a hard sell. Cap frequency on the long audience, or you'll wear the same people out.
Does anyone have numbers showing the long window actually converts, or does it just look good in audience size?