My transition from Digg to reddit was a 3 year process.
I made a reddit account immediately. Barely used it for a year while I basically still begrudgingly used Digg and also used other sites like stumbleupon and Tumblr.
Year 2 was a pretty even mix.
Year 3 I made a reddit account Id end up using for like 10 years, daily. stopped Digg, and others, held onto Tumblr for porn til pornpocalypse.