Yeah, it’s usually not procrastination when it comes to legal deadlines. It is very common in many practices to purposely file on the deadline for a variety of reasons. Ripe for mistakes.
Even disregarding legal tactics, unless you're actively loosing money waiting on a result, there is little benefit in filing early. Legal research is never really finished. It would really suck to file your appeal, then have someone stumble upon some other argument you should have made.