How much maintenance time did it take to make an F4U Corsair ready for another flight?
Far more than that. Try 50 maintenance hours per flight hour. 


  actually finding a reliable source on-line has proven to be a bit difficult. RNZAF, pacific maintenance 58 man hours per flying hour. NZ based (training) F4u 50.5 man hours per flying hour. P51s NZ based (conversion and training) 36 man hours per flight hour.


Piston engines (esp. WW2-era high-performance fighter engines) are very maintenance-intensive compared to jets.

Here's a comparison of various military aircraft types:

Saab Draken.- 50 to 1
Eurofighter....- 9 to 1
F-14............. - 24 to 1
F-18E/F........- 6 to 1
F-18E/F........- 15 to 1 (different source)
Saab Gripen..- 10 to 1  

C-17.............- 20 to 1
F-15A/B........- 32.3
F-15C/D........- 22.1
F-16A...........- 19.2
F-117...........- 150
F-117...........- 45 (after improvements, post 1989)
CH-46E........- 19.6 in 1995 GlobalSecurity.org
CH-46E........- 27.2 in 2000
CH-53D........- 24.8 in 1995
CH-53D........- 27.9 in 2000
F-20.............- 5.6
A-6E............- 51.9
F/A-18C.......- 19.1
B-2..............- 124   

and you can see modern fighters require far less maintenance hours/flight hour due to several factors:


improved systems that require less frequent maintenance 
design improvements to make maintenance take less time (better access, more line-replaceable units)