I have done that many times. I ride SPD-SLs on my road bikes, and SPDs on my tourer. I've also toured extensively on platform pedals, and with toeclips.

I'm a big fan of SPD-SLs or other road pedal systems for performance cycling. The three-bolt, bigger platform, system makes for a more secure feel when you're putting out a great deal of power in a sprint, for example. And road shoes tend to be lighter and stiffer than those made for SPDs.

But the issue is intensity, not distance. At the intensities one rides when touring there's no effective performance difference imo. On a long tour my typical daily mileage might average 50 or 60, but it isn't uncommon for me to throw in a > 100 mile day. I have never had a problem with SPDs for these distances, and using them limits the number of extra shoes one has to carry. As does touring on platforms, of course, which is also perfectly fine as long as your shoes have appropriate soles. Though in those circumstances I do like toeclips, which even if not tightened serve to keep one's foot in the best postion on the pedal in, for example, wet conditions.