Another fly rod question...when is the use of a stint warranted? What are the benefits?

Building a 9 ft, 10wt rod. Planning on a 2.5-3" fighting butt as well.

Are stints installed typically to hold a reel seat and butt. Use a stint for the both, just the fighting butt, or none at all?

I don't use them, the fighting butt material on the end is usually thick enough to add enough length to protect your tip in the tube. I would only use one if I changed my mind, after the fact, on whether I wanted a fighting butt.

You'll not like this answer - it depends.

I've never needed a stint for both reel seat & fighting butt. A stint for both would be a very long stint.

With regard to the fighting butt, suggest you first ask yourself for what purpose do you need a fighting butt and if 3" (which is a bunch) is too much. Understand a change of heart after the installation will not be a lot of fun.

Finally, I do not favor removable fighting butts (which excel at being lost), and I was taught all sections of a fly rod ought be the same length. So, depending on the fighting butt design in terms of length and design, and assuming the fighting butt design is such that simply shortening the blank's butt section is not an option, then yes, a stint can be a blessing.

Told ya you would not like this answer.

I install a stent (or stint) only when I want to reduce the butt section diameter in the position where a wood reel seat will be installed. Particularly helpful when building on fiberglass blanks. With or without a fixed fighting butt I usually make all sections of equal length.

"The greatest barrier to discovery is not ignorance, it's the illusion of knowledge" - Daniel J. Boorstin

There is no reason that the butt section needs to be the same length as the others. A removable fighting butt often makes it so all sections fit a tube. In 50 years, never lost one!