Since everything is in a projected coordinate system and no projection would be needed to send the output to a new coordinate system.
You have limited the extent otherwise since the number of cells times the time layers must be less than 2 G.
You used a neighbor option, which will slow things down by an unknown amount because of average calculation.
You didn't set a parallel processing factor.
That would leave, ... it is working but is slow as .... (the stuck at 100% means nothing really, it probably came up fairly soon in the process)
You should check with your Window's system monitor to see if ram useage is buried near 100% most of the time and whether you are getting a lot of disk read/write activity.
More ram would help if it is indeed working and parallel processing in the presence of lots of ram would speed things up.
Having said all that, if nothing is happening in your system monitor, I suspect you can (or have) stop the process
... sort of retired...