This time, I was determined to finish the Minsc quest, but my earliest saves were too recent to allow me to make the stronghold before Minsc blew up. Fortunately, a bit of judicious editing of the save game file can extend the time available to finish Minsc's quest before he loses it.
This solution requires the worthy Infinity Engine Savegame Editor, which is an older .NET application (1.1) written for Windows XP. I've had no problems installing and running it under 32-bit Windows 7. Have a spreadsheet or calculator handy as well.
1. Run the IESE and select your game type. Select Baldur's Gate if you've installed BG1 only; Shadows of Amn if you're playing BG1 under the BG2 engine.
2. Click File/Open and load the latest save game prior to when Minsc loses it (any save game will work, but using the latest means you won't lose much ground).
3. Click Edit/Party Infos. On the Global Data tab, note the Value field in the Time section. It should contain a moderately large number, which represents elapsed time in the game in some unknown scale (roughly, but not exactly, game minutes * 5). In my 20 hour, 20 minute save game, the Time Value was 150061.
4. Click the Global Variables tab, and locate the variable named MINSC. Its value is a somewhat larger number that represents the absolute time in some more precise scale (roughly, but not exactly, Time Value * 15) when Minsc will lose his marbles. I believe this variable is assigned when Minsc joints the party, and is calculated as (join time + some duration * some factor), as it remains constant once assigned.
5. All that's needed to extend your quest time is to assign a new value to the MINSC global variable. Take the Time Value from step 3), double it and multiply by 15:
150061 * 2 * 15 = 4501830
In game terms, this gives you roughly the same amount of time as has already elapsed since Minsc joined the party to finish the Dynaheir quest. Click the Set button, enter your new Value and click OK.
6. Click File/Save As, enter a new Savegame name, and click Get New Number, then Save, to avoid overwriting any of your prior saves. This way, if something goes wrong, you can always return to your original saved game.
Obviously, this technique is open to abuse, and I haven't attempted to discover the outer limits. My goal wasn't to radically change the outcome or order of quests, just to buy more time to finish a single quest line. Caveat emptor, and enjoy!