I'm an older DJ, too, and agree with RKTek regarding the increased baggage women carry with each passing year. The eligible amount of women also depends on your locale and your purpose. (Usually metro areas have larger # of eligible women at higher ages due to careers and demographics.) I have found that many women are career oriented, perfectly fine, and are waiting longer to get married ... into their 30's.
Don't forget, as a DJ, heck, as a man, you have many more options vis-a-vis eligible ages of women than most women do. If you are a 40 year old guy, your choices are from, say, age 21 to 45 which is a huge spread. Finding someone compatible at any age is difficult, but I would never let age be a restriction. Not only that, but as an older DJ, I get more poontang now than I ever did then.
Where were all those sexy 25 year olds when I was 25? Answer, they were with older dudes like I am now.
Are these LTR material? Maybe, maybe not, same as in any age group.
But, to find the right women, you have to diversify. If you are looking for a specific type of woman, you need to go where you are more apt to find them.
If you want to find a Baptist, you have to go where the Baptists are. You want educated women, take some adult ed courses. You want firm little HBs, play in the coed volleyball league. I have found great success in political groups -- the Young Republicans or Democrats groups (the Repubs are hotter in my experience, the Dems are too crunchy, but you have to pick which is your cup of tea). And, then, the world is your target, you should have your eyes peeled constantly -- some fertile hunting grounds are supermarkets (especially the health food ones which all the hotties seem to go to), bookstores, coffee shops, heck, just walking around, the world is your oyster my brother.
You should continually be building your bullpen with relievers. (See my prior post on building the bullpen.)