Several liners have used convention tickets on dates completely unrelated to the convention they were purchased for. All reports I’ve heard (and experienced) were that the tickets do not have dates attached to them, except the year-end use by date.
I really haven’t seen any statements they had to be used within the convention time frame and I agree seeing that would make me a little nervous as well. I just checked out a few different convention ticket links and the only restrictions/warnings I saw were tickets needed to be used within 14 days of first use (as has always been the case with non-tiered regular tickets) and must be used by 12/31/2020.
When digging into the detailed convention site terms, I saw the use by date there was 12/31/2019, so once again Disney confusing people.
I do think it is still safe to buy convention tickets, but I understand buying 9 tickets ups the ante. I think if it made me nervous I’d weigh the savings, ticket use flexibility, and free extra WP day against how much I’d worry about it. Plus I’d be sure to check all of the regular resellers and see how much savings I could gather at those.
In general, I think not worrying is a valuable thing when laying out so much money.