The problem with letting an ehxaust gasket/turbo gasket leak go and keep driving is that the mating surfaces can "erode" and cause a burned area on the cast iron. This will prevent the new gasket from sealing properly and will allow burn out sooner.

It is NOT uncommon for ex manafold and turbo bolts to come loose. They are constantly exposed to HOT and COLD expansion and contraction.
My DODGE Cummins loosened the ex manaflod bolts.

I would drive it as little as possiable until you fix it. I haven't R&R'ed a 2.5 turbo but the 3ltr 5cyl wasn't that big of deal to R&R. My $.02

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.