They can repeat more than two.
3z
3z/3toe
3f
3sal
3r
3toe/3r
that's 8 (for a ladies performance)
men...
3a/3toe
3z
3f/3toe
3a
3sal/3r
3r
3sal
10 (like Philippe attempted at the 92 worlds)
The Zayak rule allowed only two triple jumps to be repeated, and they could only be repeated in combination. Honestly, I haven't kept up with the rules lately, but back in the 6.0 days -- certainly back at 1992 worlds -- skaters could "legally" do only eight triple jumps in a program -- and doing eight was only possible if you were doing all six different kinds, because the rule allowed a skater to ONLY repeat two different kinds of jumps, and any repeated jump had to be used at least once in a combination or sequence for it to be allowed to be repeated. (That's why the "maximum" that Kwan, and the other ladies, were doing all those years -- unless the lady was Ito or Harding -- was seven -- because they were doing only five kinds of triples and only two of those five kinds could be repeated, meaning a maximum of seven -- the Meissners, Asadas, etc., of today can do eight-triple programs if the same type of Zayak rule is still in force, because they could do all six kinds of triples and then repeat two kinds.)
True, the rule only said any jumps that were over the six different kinds and two "repeated" in combo/sequence would "not be counted" (in other words, there was no penalty listed, just that the judges "wouldn't count" anything over), but that rule was in place. So, if Philippe actually did triples on all the jumps listed as triples in the program outlined above, then if the judges obeyed the rules, the solo triple loop and solo triple salchow would have been "not counted" by the judges, since they were both "repeated" jumps when two jumps had already been repeated, and therefore would not have counted.
Boitano had several seven-triple and/or eight-triple clean performances -- certainly the 88 Olympics, if nothing else.
ETA: Oops -- gkelly already answered this, so this is just a reiteration of gkelly's response!