How many keys are you trying to generate?!
For me to make a 2^32 DB, it took over 5 hours. I used the low memory script and wrote to file 2^26 keys, roughly every 5 minutes. 64 (2^32 / 2^26) x 5 minutes = 320 minutes
Also, just for info, a DB with 2^32 values = 524 MB (incredible!)
Can you share your script to create the database file?
I want to create a file of size 2000000000 keys to test on puzzle 65.