Use the maximum weekly miles you've done so far as a baseline. If 150 miles is the max, that works out to around 5 days of 30 miles a day on tour, with 2 rest days a week. The second week you can reasonably extend the mileage around 10%, so 165 miles. If the area you'll be touring is much flatter than your home turf, you'll be able to go somewhat further (but from what I recall of geography, I don't think Nice to Milan is likely to be flat...). A 50 mile day is probably a reasonable maximum for you right now.

That's much less than an experienced bike tourist would plan on. But a lot of experienced bike tourists have *practiced* doing much longer rides, so they know their bike works well for 100-150 miles in the saddle every day. You don't know how your bike works for those sorts of distances, so shooting for them is a good way to get hurt. Also, doing 100 miles every day doesn't leave a lot of time for sightseeing .

After you've completed this tour, you'll have a much better idea of how well your bike fits. And you'll be in much better shape for long rides. Fix up the bike if any problems develop, and for your next tour you'll be able to go longer

Oh, and remember riding with a load changes things. You *do* feel it. Don't be surprised if a distance that felt easy unloaded feels much harder loaded. If you can get a loaded practice ride or three in before you leave, it will help a lot.