Honestly it all depends on you. But I would not recommend you to go do it at anything less than 160cp in case you do complete it and get a good weapon at crap level.

nnargun wrote: »

Another question:
For how long does it save my progress within the same stage? Like when I leave for repair.

If you leave the instance (i.e., if you port out of Maelstrom, if you log off, if you disconnect, or if you crash), you have 5 minutes to get back into the instance (not into the actual fighting arena, but just back into the lobby). If you take longer than 5 minutes, then the instance is reset, and you'll be resuming from your saved quest. When you lose the instance, you will lose any progress within the stage (you'll be starting the first round of the stage), and you will also not qualify for a score or for Flawless.

This means that if you complete a stage and want to port to your home to make more potions, as long as you return in 5 minutes, it would be as if you had never left--you'll still qualify for a score and you can still qualify for Flawless (assuming you hadn't already been disqualified from those earlier).

If you don't leave the instance--if you just hang out in the fighting arena between rounds on a death recap screen or hang out in the lobby--then you have quite a lot longer than 5 minutes. Probably indefinitely (as long as you can prevent your character from being logged out due to idleness), though I think there was once when in-stage progress did reset after several hours (this was almost 2 years ago, back when I was trying to get my first clear and vMA didn't have a save feature--I placed an object on the movement key on my keyboard so my character kept walking into the wall as I went to bed for the night... this was so long ago that I can't remember).