Why not fix the leak? If it's leaking that bad it should be pretty obvious where it's leaking. When the fluid runs out, it basically just quits working. If it's been working normally when you add fluid, the internals of the transmission are probably fine.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]