when to use triplet strum

I see a lot of references to the 'triplet' strum, and there is plenty on the www about how to perform it. My question is about when to use a triplet strum ? I've attempted it on my 'go to' tunes, but it just doesn't work. Are there some specific tunes where the triplet is the appropriate strum that you could point me to? many thanks

Use the triple strum when you want to emphasize something. If you're playing a chord progression, this is usually when you switch chords or, if you're going for a more mellow sound, right before the progression loops. If you're playing a chord melody, then you can just use it whenever you feel like it.

Take this, for example. At 2:41, 2:43 and 2:47, Jake does triple strums to add some dynamics. However, he doesn't triple strum at 2:45 so that he doesn't sound too robotic. A more advanced example would be the triple strums at 3:09 to really make things cherreh.

Side note: I've seen some tutorials teach the triple strum as up-up-down. I've also seen tutorials teach the triple strum as down-down-up. I personally play up-up-down (here's a video), but use whichever one's more comfortable. However, playing triple strums as up-up-down has the added benefit of adding a down strum right before it, giving you more options to spice up your dynamics. Excluding the 3:09 triple strums in the first video, Jake does exactly that: a down strum followed by a triple strum.

Too my mind, the triple strum is an ornamentation and, as such, should be played sparingly as an accent or at the end of a phrase. It can be used in many tunes ie. See You In My Dreams, Ukulele Lady, Wagon Wheel etc.
George Formby made great use of this strum mainly during synchopated solo breaks.
A little goes a long way.
It could be that your technique is not fully developed and while playing the triple you lose the rhythm and beat.

Excellent responses so far - thanks!

my go to triplet strum song is:

By the light of the Silvery Moon

keep uke'in',

I agree with Barrytone, whole-heartedly. Any specialty strum or flourish should be used sparingly or it ceases top have the desired effect. Personally, I think songs that should incorporate a triple strum are slightly less common than unicorns. Learning how to do a proper tremolo will probably be infinitely more useful, and less time consuming...

However, that is just my humble opinion. Your mileage may vary.

A good example to listen to is "(I Love To Play) My Ukulele" as recorded by Max Bygraves, as it uses quite a slow triplet strum and not a lot of other ornamentation besides that. Unfortunately it doesn't seem to be available on You-Tube, but you should be able to get it from Amazon, Google Play, iTunes or wherever (I use Google Play). It's a fun song to play too, but some of the chord sequences are quite tricky.

I haven't quite mastered the triplet strum myself yet, so when I play that song I only throw two or three in where I can.