You can drive on ticking lifters for quite some time with no immediate damage. I have personally logged tons of miles on vehicles with lifters ticking loudly. From what I understand, it is more of a slow eventual damage as in greater tolerances due to wear, though I never experienced the end result personally.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280