The only way to really preserve them is to record the video while running the replay, replays don't work from patch to patch.
https://wiki.wargaming.net/en/ReplayIf you go to the replay folder (mine is C:\Games\World_of_Warships\replays) after enabling them and playing a game you will find some files with names looking somewhat like this
20191113_090908_PISC101-Eritrea_33_new_tierra.wowsreplay
if you click on these and drop them on the Wows launcher in your WOWS folder (C:\Games\World_of_Warships\WorldOfWarships.exe) then it will launch the replay. If you have an NVidia card with Geforce experience enabled you can record the replay by hitting Alt F9. If you use windows 10 the Game Bar can be opened with winkey+G.
video showing the process.
https://www.youtube.com/watch?v=O8lmSJCCGU8You can change the limit of 30 by using one of Aslain's mods.