I have some older Fut S148 servos in use and about 8 years when I switched from 4 cell 4.8v NiCad to using a 5 cell 6.0v NiCad in my 2.4 systems I posed the question to Bax the Fut rep who advised me that the servos would be okay on 6.0v. Then about 3 years I switched again to using Life 2 cell packs exclusively to power the same servos and so far no problems.