Quite a bit more.
Even those ships which have just left service in the past few months will need a LOT of work given it's normal for upgrades and even general maintenance to not be carried out once it's known the ship's getting decommissioned. What's the point of doing more than is absolutely necessary to keep the ship afloat when you know once you reach port it's not going to sea again?
I know this is a bit of a problem with buying used ships too, both military and civilian. Just have to look at the problems the Australian Navy ran into when they purchased the two Newport Class landing ships in the mid 90's.
https://en.wikipedia.org/wiki/Kanimb...orm_amphibious
Note it took five years to get just those two ships ready for service because the engineers kept finding problems which HAD to be fixed.
And those two ships had been in US active service at the time the RAN took possession, and not mothballed.