How long does it take to upload documents to IPERMS?

Depends on how effective your S1 is. Depends on how many folks are sending in documents to be iPermed. But, normally, it shouldn't take more than 1-3 weeks. Normally.

My batches are taking about 30-45 days to hit SM records.

In the Guard, this is the route:
unit RNCO or BN S1 batches to iPERMS
BN or BDE S1 Reviews batch
BDE S1 or G1 QCs batch and releases it to your record.

When boards are coming up, local and state SOPs usually dictate that the batch have BOARD in the batch name or comment box to expedite.
However, the process still takes as long as it takes for three people in different locations to do their job.
That could be anywhere from 48 hours to 3 months.
If you are on the current promotion list, these documents won't affect your place on the list, but they will for the next board, and they need to be in iPERMS by mid-March at the latest. So if they are not there in FEB, have your RNCO and BN S1 follow up.