or did you just mean how long in a set at any given time? In that case sorry for writing you a whole book.I have no set time for you but would argue its probably more important to do them often rather than for a long time. How long is a typical paddle out where you live? Maybe strive to double that.

It might be better to think of the blocks differently.

For me the process has been more circular (or spiral shaped if you will), rather than linear. What I mean is that I go though the blocks (also assuming I can actually do certain stuff) and then at some point I realise I now know stuff that makes me question myself and go through the whole thing again. Now the second time I'll be at a slightly higher level than the first time. And then at some point I'll come back again...

Or sometimes I go though them in reverse. For example: I want to improve my snap. Then I realise I need to do a better bottom turn to do a better snap so I go do that block. Which makes me realise I nead to take a different line from takeoff to do a more U shaped takeoff. etc. etc.

I'm sure you've gotten my point by now. There is no set timeframe. Do what feels right and at some point you'll probably come back tot he same place, only with more knowledge and skills.