The honeymoon period with my ex lasted about 3 months before turning into hate fest. The idealization returned several times, usually if I tried to dump her but then took her back. This would usually last about a month before the rages really started back up. I do not believe the idealization is like some sneaky tool they use to get their claws in us. They genuinely do idealize us, though they may exaggerate in what they say to make us feel good about ourselves, but I think that's more to do with them and their need for approval/acceptance.
Also, when she recycled me did a new idealization phase begin each time or was it more to soothe her pain from whomever she broke up with?
One of the false beliefs of a pwBPD is "feelings are facts." So if being with you did make her feel better and soothe her as you say, then it's likely she associated you with that feeling, which means you must be all good. It's like anytime I took my ex back after trying to break up with her, she would be relieved and feel better, therefore I must be all good, and the idealization would happen again. It was a very sick cycle.