ed downs

OK, OD it is. Thank you

And as a newcomer here I must say how refreshing it is to get answers to the question asked without all the rude ego displays you get on many forums. Another plus point for Triumphs. Thanks to all

I am looking to buy a Spitfire to do long cruises. I had thought to get one with OD because of the extra gear leading to less revs when cruising and a saving in mpg. From what have found out OD changes top from 1:1 to 1:0.8, and possibly mpg from 30 to 35.
In these forums it is suggested that having OD adds £1000 to £1500 to the price. If I do about 10,000 miles p.a. and the above figures are roughly right that would be 3-5 years to get the outlay back.
There are also a lot of threads here about problems with the overdrive.
So, is it worth it, the extra money, the possible failure?
Any advice would be very welcome as I am new to Spitfires and the last time I used an OD was in the 70's, in a Dolomite I think.