LOLOL, film cameras, DSLR's, Canon focusing screens

Was going thru the closet and pulled out old 35 mm film cameras. Went to remove batteries so they don't corrode and ruin cameras. Have found that batteries in electronics corrode if not used often. Have Canon slr 35mm camera w telephoto lens that haven't used in 20 yrs. Old tech but works great, don't want to throw either. Only worth maybe $100.