Speaking as a runestaff-Bard who just turned the MC:Mental up to 40 ranks (had been 30)... I do! :)
However, I do it in steps of 10 ranks. That's my entire point: why stop at 24 or 25? Get 6 (or 5) more, and get the PAYOFF.
(I also counsel Sorcerers, and other Bards, though not Empaths now that they are no longer Mental, to go up to 20 ranks/90 skill in their <second Realm>, and STOP, because going to 30--as I would otherwise suggest--does nothing for them unless they kick it up to FORTY [second Realm only counts half].)
At 105,500 experience to make level, using GSWiki's estimated 105.5 hours (at 1k/hour average), figuring 25 mana pulses per hour (due to variable timing, and to keep the math pretty), is well over two and a half thousand extra mana for use, just for that one level.
I agree absolutely: it comes in as a trickle.
But mana is mana.
I mind me of when we were sussing out Bardic medley Renewal times: because I had started with a high CHArisma [now, INFluence], my renewal was something on the order of 2 minutes longer than my contemporaries (or "as long as someone 30-50 levels higher"). I compared medley renewal costs for identical sets of songs, even against someone with a MUCH higher DIScipline (the stat that reduces the Multi-Song Penalty). 100% true: his MSP was lower than mine... but I paid it so many times fewer, that I came out ahead on mana (by thousands), even singing one song MORE than he did.
(I use "2 minutes" as a significant point in bard song durations, because even a theoretical capped Erithian with maxed stats and Lore will only have a medley renewal of 11:47; max out the Enhancives and it is only 14:47. So, when comparing two Bards in their 20s, with a "two minute" difference in renewal time, is a significant fraction of the "less than 12 minutes" possible for a capped character of the best possible race for time.)