This is my biggest pet-peeve in clubs - one can work around things like a bad dancer or a dancer wanting to charge too-much by just finding another dancer - but if you get a bad DJ then you're stuck with him and he can fuck up your whole visit and every one of your dances (by cutting songs very-short) and for the most-part there's nothing you can do about it except leave or not get dances.
I SCed for 10-years b/f joining TUSCL and never once did it cross my mind to time songs - part of it is that b/f joining TUSCL I did not SC as much nor hit as many different clubs.
Post joining TUSCL and learning the finer-points of SCing, and becoming aware of different SCs, I became a more avid PL and started hitting more clubs including hitting black SCs more often - it wasn't till I became a black-SC goer almost exclusively that I got hit w/ a severe-case of song-cutting which as I learned from reading a lot of black SC TUSCL reviews, is much-more egregious in a lot of black clubs.
As shadowcat mentioned, often times in the black-clubs not only are the songs cut-short, but they are bled-together like some lunchtime power mix - in most-mixed clubs the DJ talks in b/w songs either to announce the next dancer or just say "set #2 for Lexus"; etc - this is often not the case in black-clubs where the DJ can often talk all the time often over the music and at times even stop the song for him to share w/e is on his mind - thus one can't even try to cue off of the DJ consistently talking in b/w songs.
One night circa 2012 in a small black club I was having a very difficut time trying to know when one rap-song ended and another one started - about 4-minutes into a dance w/ an ebony I decided to double-check the dance-count and to my PL-astonishment she tells we're into song #4 - I stopped the dances and just paid her for the 4 - at first I thought she was ROBing me but I decided to pay extra-attention to the music and sure-enough as best as I could tell this guy would mix in a new-song every 30 to 45 seconds as if he was in a hiphop club vs a strip-club.
This is when I got religion and became a song-length Nazi and started timing songs whether it was a mixed-club or a black-club - and to my surprise, in many mixed-clubs, although not nearly as bad as the black-clubs, songs were shorter than I thought/anticipated - in many mixed-clubs songs were being played as short as 2.5 minutes for a $25 LD; w/ teh avg being around 3 minutes; and some around 3.5 minutes - I would also noticed in certain clubs they seemed as if they had kinda like a sequence where they would play songs from 2.5 to 3.5 minutes - e.g. they would play a song at 2.5 mins, the next one closer to 3 mins, the next one closer to 3.5 mins, then back down to 2.5 mins for the next one and repeat the sequence - felt to me like I was being scammed b/c it's not as if I was paying less for the shorter songs - and also felt as if they were mixing the sequence on purpose as to not look as obvious that the songs were being cut-short.
Trying to fight for longer song-lengths is kinda an uphill-battle - for one the avg custy that just visits clubs from time-to-time probably doesn't have a clue - neither are most custies for that matter (I didn't really noticed till I experienced the supa-cut-songs in black clubs) since they are focused on the dance/dancer - also, some custies go to a club just to socilaize/hang-out/be-spectators; others focus mainly of VIP which is usually a block-of-time; others go to a club with the main-purpose of finding an OTC candidate - i.e. only those custies that like to get lots of dances are most affected by cut-songs.
When I became an avid-reviewer I would mention this a lot in my reviews particularly my black-club reviews - with time it got a lot better where now is not as big an issue - I can't claim it was my reviews and probably wasn't; I asssume a bigger part of it was me transitioning from a mostly nightshift custy to a mostly dayshift custy where the song-cutting seemed more egregious during the nightshift party-time where the black clubs in particular felt more like nightclubs or house-parties.