I like to wing it for one-nighters between longer stops, but shorten days so we can start keeping an eye out after ~3:30pm for a "zimmer frei" sign, overall have had great rooms at great prices, in Bormio I walked into a gaff and it seemed a bit pricey, and then they wanted to "upsell" me a suite, I declined and ended up in a huge room with bed, sofa, large bathroom and balcony, I think it was all they had, hence the keen upsell.
Another time we got a 2 bedroom family unit in Austria for a song, the one time it went wrong was when we hoped to get a place on a pass on our way into Switzerland and failed to find a space, ended up paying a lot for a very average room in a town centre Hotel above a multi-storey car park in Thun, but it was clean and comfy, the town was nice and we knew the risks of winging it.
With the amount of Hotels on websites now it is much easier to just book a day ahead, or even stop at lunch time and find a room, the amount of smaller gaffs on booking / hotel sites has exploded, and internet access is much easier to get than 10-15 years ago, sadly I think there are less hotels and B&B's now though.