If you wax — ZFC-recommended path. No staged plan needed, just the top waxes doing their job. 160 km is inside every major immersive wax's single-application life. A surprise shower won't change the plan — tarmac rain is just water, and a fresh wax treatment rides through it; 160 km doesn't warrant the post-ride strip that oil-over-wax demands. The baseline scenario for comparison.
If you're on oil — pragmatic equivalent. Pre-ride application of your usual oil is plenty. 160 km is the baseline test of whether your application technique is working — if you're regularly topping up at this distance, your application needs work (more oil per link, longer dwell time, then wipe off the excess).