When is it ok to cut for clones?

You can clone any time you want.  There needs to be enough vegetation for the plant to stay alive, but as long as the plant is established, you should be fine.

 

Cloning branches from a blooming plant will result in thicker, bushier plants, supposedly, which is supposed to increase yield or something.. You can take cuttings all the way through, really. I've seen people cut off a nug in week 4+ and root it, but I wouldn't do it myself, as I would rather just have the original plant as a mother to create other clones, instead of blooming her out.

 

Don't clone a flowering plant for two reasons.  First, NEVER, never, never cut a flowering plant.  It is more stress than you want to give it as it will more than likely reply by mutating hermaphrodite.  Second, If you take a flowering plant and throw it back into veg (as you would be doing with a flowering clone scenario) it is going to "monster crop" on you.  This may seem like a good idea, until you grow one of them.  They grow all over the map and are a total nightmare to trim.  If you want a larfy mess, go idea, but in my experience I would not recommend it.  
 
VH, you need to stop talking out your ass.  IF you have experience with something, share it.  Misinforming blades with things you have "heard" is just going to confuse people and send them on the wrong path as you have just done.  Not trying to be a dick, but you need to advice more from experience and less from what you have "heard".

 

I cloned week 5 flower once just fine ...took a couple small scraggly branches from a blue dream and they rooted fast in my bubbler but took like 6 weeks to reveg and grow..they grew out fine but I cut all the shit off and trimmed them back to 4 colas...got nice clones of em too but yea its better to get some while vegging

 

Of course it is possible to make it work.  Anything is possible.  Is it a good idea, probably not.