put an amount of time in on
put (some time) in on (something)
To invest some amount of time to something or some activity. I've put months of my life in on this project, so it's really gut-wrenching to see it get canceled at the last minute. You can't just put an hour or two in on an instrument and expect to suddenly master it.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
put an amount of time in on something
to spend an amount of time (doing something). You put how much time in? I put in four months on that project.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.