Thank you for your reactions. I will have my tubes measured next week. The guy I bought them from said tubes were 3/4 year old and therefore 'as new'. After contacting CJ's famous consumer service that they last about 1000-1500 hours, so this will probably last 1,5 years or so.
I compared my CJ pre-amp with an Audio Research LS 8 mkII. That's where the comparison of a dry sound came from.
I still have to get used to 'planning' my listening sessions with a tubed component. I used to listen a lot of moments (almost every spare moment), but I keep getting the feeling that it's not good switching the unit on and off all the time...
I'll post an update as soon as I know more.