[drc]

You can display stuff as long as you limit the overall light-- limit time, intensity and exposure to light. For example, a windowless basement room is better than an upstairs porch or sunroom. Turn off the lights when no one's in the room. Maybe don't have really bright lights in the room. Some museums have dimmer light. Incadescent lightbulbs are best-- the old fashioned oval bulb kind. If you want to go whole hog, use UV protectant glass. UV glass blocks out most of the UV light which cases a lot of fading. If you have baseballs, many of the new baseball cubes are UV protectant. You could also drape cloth over the display when they're not in viewing use. That's what a lot of card dealers do at shows with their display cases.

If you have a basement or largely windowless room where you only have the lights on when you're in there, you're probably going to be okay. You're both enjoying the display and limiting the light exposure. The major problems happen with lot of exposure, like hanging a rare poster in direct sunlight in the porch. When the owner of this poster goes on vacation, the poster gets 7 days of direct sunlight and no one's even there. If you don't have a sunless room (every room except the bathroom in my home gets sunlight), then draping in black cloth is the equivalent of turning off the lights.

Lastly, different things are effected differently by light. Autographs are the most sensitive, while a bat, glove or toy is less of a worry. Even if a glove or bat lightens a bit, it may not effect the value. I don't think displaying a bat collection is a worry.

I have one or two nice items displayed in my home, but have them in an area that gets no direct sunlight from windows. I have a vintage movie poster in a hallway, and an original color photo on a wall that gets light but no direct sunlight from windows. I've also had an autograph in the less lit hallway wall for several years, and it's still in good shape. On walls that get lots of sunlight, in particular direct light, I don't have anything expensive. I live in a second floor condo that has big windows and gets tons of sunlight, so my place is a fair testing ground.

I don't think you have to be a zeolot about it-- just consciously work to limit the overall light. Pulling the shades and turning off the lights when you leave a room will probably cut about 70% of the light right there. A collector doesn't have to plaster over windows in the den in order to display stuff. Even the Louvre has lights on during visiting hours.