My rule of thump and stomac feeling is not cropping to far under 20 MB (300 dpi, 8bit, tiff). So you still can print it at a reasonable size (A3). If you shoot jpg, the upsizing is less before seeing artefacts and alike. With scanned slides it's even narrower - about 20% upsizing, then it starts to become to ugly. If unsure make tests on your printer at home or send a heavy crop to a lab and order a a3/a4 print.
Cheers
Berni