The foam light seals in film compartments will degrade and crumble over time, leading to light leaks. If light leakage is detected, timely replacement is necessary (you can purchase these DIY foam seal kits tailored for specific camera models).
For film enthusiasts, maintaining and updating cameras to ensure optimal shooting performance is remarkably convenient.
Most classic film SLR cameras use foam light seals on their back covers, particularly models from the 1970s to 1990s:
(Nikon): FM2, FE2, F3, F4, FM10

(Canon): AE-1, A-1, F-1, FTb

(Minoltx): X-700, SR-T 101, XG-M

(Pentax): K1000, MX, ME Super

(Olympus): OM-1, OM-2

(Yashica): FX-3, FR series

Some rangefinder cameras also use foam seals for light-proof back covers:
(Leica): M3, M6 (early versions)

(Konica): Hexar AF, Auto S3

(Canon): Canonet QL17 GIII

(For Voigtländer): Bessa R series

Many compact film cameras employ foam seals for simplified light-proofing: