I always start by reading the instructions. For Ilford multigrade developer and Ilford paper, it says 1 minute for RC and 2 minutes for fiber. I've been doing it this way with great results for over a decade. Part of the key for good darkroom results is to be CONSISTENT. The prints are in the tray face down so any extra safelight exposure is minimal. And if 30 seconds mattered as far as safelight exposure, then my safelights would not be safe.
hi bethe:
i never leave them face down because i want to see how they are comming up in the tray.
maybe i am lucky that my safelights have never caused trouble but i wouldn't ever leave it facedown ..
its always been flip it ( or if i am doing multiples, have them back to back and face to face and shuffle the groups of prints )
and make sure the tray is rocking. the just plopping the print in the tray and leaving it there is what i have found to be the biggest mistake
people new to print developing make. the print does the equivilant of "stand develop" and is sometimes splotchy and the contrast is all screwed up,
parts are developed more than others, there was an air bubble on the paper ( or under the paper ) ... and it comes out bad
when i was working for a busy portrait studio, we had tray rockers, they were noisy, and corroded ( and actually broke when i worked there after 50+ years of use 10 hours a day 5-6 days a week )
they were a huge help when dealing with consistant tray agitation .. it was just the flipping over 5 or 6 times and watching to see when the image appeared.
of course there are as many ways to process a print and develop film as there are people doing it, and in the end if someone is happy with their results that is great.
and as you said, consistency is key // so it is a huge YMMV