I have no idea what an average time is. Sometimes it's something they don't reorder and you never get it. I've had one item show up a few weeks after I ordered it.
If it's something you really want, of course it's worth it to waitlist order. Why wouldn't it be? If you really want it and it comes back in stock in the 45 days, you'll get it. If it doesn't, you won't get it and you don't get charged, so there's nothing to lose. If you put yourself on waitlist for an item you change you mind about, you can cancel the order.
I doubt there is an "average" time. They just cancelled one of mine from June. On the other hand, I've had items ship after just a week on waitlist. It could be any length of time.
I have waited up to four months and as little as a few days. QVC has cancelled my last waitlist orders from July, not expecting any more inventory.
I would say go on WL if you aren't in any real hurry to get the item. You may or may not receive the item but you aren't charged until they ship so if the item doesn't come back in stock you won't be charged.
