Help How long do you get from your slicks

[stradman]

Hi guys, going to a 4 day track event in about 10 days.Its not racing but just HPD with some buddies(with some serious toys!) on track. Its fairly casual with lots of breaks and usually do 25-30 minute sessions at a time max, maybe 5 sessions in morning and 5-6 in the afternoon. I'm certainly not a pro and very much a rank amateur however I give it as much stick as I can! So how many sets of slicks would you say I would need for those 4 days?? I've currently got 2 sets of Pirelli DH slicks at the moment.
Many thanks guys