I've taken part in the last 8 PBPs and finished the last 7, but I only ever bought one ACP PBP jersey. I guess I must have felt a bit flush in 2007, not foreseeing the impending financial crash. I hardly ever wear that jersey, even though it actually looks ok, fits ok and I finished the ride, so I don't plan to buy any more commemorative jerseys.
Regarding the PBP water bottles, I used the 1987 PBP water bottle from the ride I didn't finish until it wore out, but I keep the unused water bottles from the last 7 PBPs that I finished in a display cabinet. I must admit to a further historical water bottle irregularity as I used two LEL A68 Club water bottles in the mid 90s when I had only ridden the LEL A68 route once.
Despite this I wouldn't wear a commemorative jersey if I hadn't completed the ride within the time limit.