Just a note that for the Viking cruise discussed there are currently 120+ people signed up through Kevin/the DIS and there is room for plenty more ... and if it was not mentioned on a podcast I would not have known about it - and my wife and I did sign up for it (and glad we did then as we got in at one of the lower room rates that is no longer available)
As for other podcasts - I also watch a number and some of them also promote their sponsor multiple times and in the middle of the podcast not just at the beginning, etc. (so different ways to do it)
I mean, at most it takes up 10 mins of the podcast (probably a lot less most weeks) and you know it is at the beginning so you can skip it if you don't want to hear it.
Obviously everyone is different and if it is a big deal to you, so be it - I just don't get why someone talking about a trip for 5-10 mins (max) would cause you to stop listening to an entire podcast that you enjoy