I've replayed Platinum five times and completed it three. I remember deleting and replaying since I hated my previous team, made silly mistakes or just in general forgot what I was even doing. I'd be standing somewhere, usually a cave or a building, walk outside into a city that chimes a bell in my head but forget what I was even doing there. Yeah I'm a pretty forgetful person when it comes to remembering storylines and plots. XD;
On my first go of Platinum back in 2009, I remember teaching my starter two HM moves and grabbing all the Pokemon in sight even ones like Bidoof and Kricketot. I didn't know any better, I was unfamiliar with the franchise at the time and tested things out, my first playthrough of Platinum was sort of like a scientific experiment, to see what was good to use on a team and what was an absolute no no. I think I actually somehow managed to beat Cynthia, probably with the help of Giratina but afterwards the postgame was too difficult for my 8 year old self and I restarted.
Fast forward one year, I'm playing yet again with a three man team. Empoleon, Rapidash and Luxray. I seemed to have forgotten all of my Pokemon knowledege and did similar to the thing before although I did remember to pick up a HM slave instead of using my team. Although the usage of three Pokemon was really hard for me, I ended up beating the game with a highly overlevelled team and restarted yet again because I was bored of that save file.
Fastforward another year I actually played Platinum with a full team of Pokemon, I was completely happy with. I beat the game fairly easily and even attempted to catch them all, I had a 100 or so to go before my Pokedex was complete. I did everything I could possibly do, get all the Pokemon I could possibly get and there was nothing else to do except spend all day long beating up trainers in the Battle Frontier, so I just left my game card on the desk for a while.
The fourth time, my sister didn't want her Platinum so I claimed it and started yet another save file for a challenge. I ended up getting to around the second gym but getting bored and finding it difficult to manage time with playing the game, so I ended up quitting that.
Fast forward to now I'm playing for the fifth time and currently doing well so far. I've enjoyed playing through the beginning and hopefully I'll finish, I'm now around the first gym. So yeah that was a recount of all the times I've replayed Platinum from when I first got the game to now.