Hi Bill,
Welcome to the forums!
I am also working on riff practices. I am fitting these into my usual technique method that I just posted in another thread.
I practice these individually so I can work on bend accuracy, and also I fiddle with timing to fit into whatever I think they may fit into. I keep these to 3 minutes to combat my mind getting too sloppy. I am about to replace 2-3 that are good enough with 2-3 that are next in the lesson plan.
One thing I do need to consider now, is adding some way to incorporate the ‘good enough’ ones in an active song or backing track session.