to optimize informative value and lower server-load at the same time,
the possibility of a growing ping intervals of the heartbeat signal would be good.

(edit: @diosmosis has also proposed the main thought behind it in #8213, here it is again in a little more general way with more explanation why it's really needed and with a concrete example)

Use-case:
At the beginning of a one-page-visit it's very important to have very short intervals to understand why the visitor was leaving (especially on one single page visits)
But because of server-load, one could not keep this very short interval within complete visit where it is not needed anymore.

A) very short: only seen very first design impression could be the reason (or site does not load completely e.g. because of a blocker software and looks broken)

B) short: only headline, Image, first sentence could be the reason

C) middle: content was in general not that interesting to read everything / take action

D) long: got all information but takes no other action
e.g. because he got everything he was looking for
or even seeing/reading everything it was not motivating to take action...

=> One idea to set this up, is giving a second value
to the setting of the the default heart beat interval
( _paq.push(['enableHeartBeatTimer', 2]); )
which defines some kind of a growing factor which is multiplied to the interval used before.

the result could look like: