45 miles, but there is a sauna...

While I understand the sauna on arrival, the sauna before going home could cause dehydration and is probably best avoided.

Going in a sauna never causes dehydration if you do it correctly. Always drink while you're in the sauna, drink cold water with ice and you can stay in longer. By longer I mean when you're starting out some people can't handle staying in very long.

If you can, eat before you go in the sauna, like an apple and a handful of nuts. Drink iced water the whole time you're in there. If there's a cold plunge, alternate between the both of them.

When you're doing that many miles you really need to contrast bathe at first until you get used to it. End on heat when you're about to go riding, on cold when you're done with your riding.