Reachmahjong.com

This is a hand I saw playing: East 1, 0 continuance, you are dealer and about to make your 15th discard; this is your hand:

draw: dora:

In the ponds you can see three and two , so your wait is bad, and in your pond you have just one bam, .

I'm not sure if I'd riichi: I already have two yakus, so I can already ron: this is a 3 han ( ) to 5 han ( tsumo) hand, so 3900 to 8000; with riichi, it's 7700 to 8000, more if I hit tsumo, ippatsu or ura-dora; on the other hand, I have very few waits and very few turns, so I'm betting 1000 points on a handful of tiles, and I'm warning my opponents I'm tenpai (with a pond that says, "Beware bams").

(The player riichied, draw and hit two ura-dora, for a baiman.)

You have +/-17 turns per hand.
Declaring riichi at the 15th discard is very very late, and you already have a yaku.
So, there are too few chances to improve the hand be declaring riichi here.

However, declaring riichi is still interesting to warn the others you're tenpai, and hope they'll fold... That being said, it's of little use that late in the game.

==> No riichi for me.