So lately I haven't been as active on site as I used to be and I got another loyalty box. Do I need to open it right now? What happens if I go another year and this one sits untouched? Do I lose it?

I've seen people with HUGE hoards of Loyalty Boxes that they don't know what to do with so I'm pretty sure that if you don't open the one you have, you still get another one, and the first doesn't disappear, so take your time in deciding what to do with it

There's no problem keeping it for ages - I've usually got the last two or three unopened because I'm very indecisive on what to use them on. If you go a further year and get another one, it just joins the previous one(s) in your inventory.

I use them to make gold accounts. I had four the other day, and I traded two in for gold account tokens. And I already had a gold account token. I've enough for a year's worth of gold account. :)

They never expire and having one doesn't prevent you from being awarded another. I've been saving them to use the stat totem once my pet hits tier 13. Unfortunately, you can't tuck them away in your vault so they can end up sitting in your inventory for years.

they are locked to your account so they can never be taken or destroyed or accidentally moved to your shop or donated or fragged. the only danger is deleting them, but you'd have to manually click on the box and then select delete. other than that, it'll always be there until you use it.

(and personally i find the pet slot most valuable, but what you want to use it for depends on your play style)