You can tell the motor mounts are bad by looking at them to see if there is brown fluid leaking from them. Yours are certainly bad at 145k. My w210 vibrated and buzzed like hell and after I replaced the motor mounts you can't even tell the engine is running while in the car.
You probably won't hurt anything by leaving it alone but the car will be much more enjoyable with new mounts. Lots of info on the subject if you want to do it. Took me about 3 hours.

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tgmiller77
1997 Land Rover Discovery 158,000
1995 E320 Wagon 132,000mi
1999 E320 Wagon 97,000mi