Do I need to worry about keeping my equipment collection in DQ9 below any sort of limit? I haven't seen any indication in-game that I'm running out of space, but I'm not sure if it's actually infinite or not, and I don't want to risk losing an item because I accidentally maxed out my inventory.
Your bag can only hold 99 of each thing, for both equipment and consumable items. If you have fewer than 99 of something, you can buy up to 99, but not above.
My strategy is to periodically sell down my inventory to one of each standard equipment and 50 or less of replenish able consumable items. I can always use more gold in the bank. I haven't yet gotten near the 99-each limit for really rare stuff, but I figure I can address that with Alchemy when the time comes.