The group's singer Jason Lytle has no idea whether the bearded bunch will keep going past this reunion.
And the frontman wants to see how things go before committing to anything in the future.
"Everyone in the band has their own thing going on, so we are just going to do this and come out the other side, then reassess things at that point," he says, speaking ahead of their O2 ABC show, which is part of the No Mean City festival.
"I am not really in a hurry to sort anything out. I like being on my own, travelling quick and stealthy and just being able to dart off by myself whenever I want to.
"So I am not superfond of travelling in a big group and being part of all the logistics that go with it.
"I actually like the idea that Grandaddy will come to an end, but maybe we can look at doing more shows later and maybe even look at new songs. I want to keep it open."
That free spirit nature endeared the California fivesome to many during their several years together, during which they released four critically acclaimed albums of indie rock, and even cracked the UK Top 40 with their single The Crystal Lake.
Commercial success was never the main motivator for Jason, but the band's return to the live stage after six years away was sparked by a very practical reason, as they were offered a deal too good to turn down.
"We had a really good offer from a festival in San Francisco and I guess it gave Jim (Fairchild, the band's guitarist) the idea to take it really seriously. He presented me with the idea that it might be fun and we figured we had to treat it as having some fun."
However, it is not just a case of money, money, money motivating this reunion.
Jason admits the group clicked when playing together again almost immediately, and that is why they have added extra shows.
"Hanging out with the guys and playing to super enthusiastic crowds means there is no weirdness there," he says.
"We are getting something out of it, and they are getting something out of it.
"We are getting paid, which helps our efforts, and there is nothing sad or pathetic about the reunion."
That mention of the energy from the crowds Grandaddy are playing to brings the conversation neatly around to Glasgow, and tonight's show.
The reason Jason appreciates the city so much comes from liking the lively response the band always receives here.
"The shows are always super insane and the crowds are really enthusiastic," he adds,
"It's fun to factor that into the whole experience. When you try to enjoy yourself on stage it can really make a difference when there is enthusiasm coming from the crowds.
"I have been there a few times on my own and, while part of me thinks that cities are beautiful, I tend to prefer more breathing room when I am travelling.
"Glasgow is up there as a lovely city, though."
After these Grandaddy gigs, Jason is back to being the lone wolf, with a new solo record, Dept Of Disappearance, out in October.
It is an album cinematic in style, and the singer says he writes his solo stuff exactly as he would Grandaddy numbers.
"There are multiple similarities between Grandaddy stuff and Jason Lytle stuff, but I think of Grandaddy songs being like guilty pleasures, with over the top sonic stuff going on," he says.
"I think I have a pretty set program in my brain about the sort of music I like and get a charge out of, so it is only natural there is a lot of similarities there.
"Most of the time I am trying to allow something to happen while taking the details about what I want from my brain and getting them to come out the other side – I don't want to take it apart too much from the original idea."
n Grandaddy, O2 ABC, tonight, £18, 7pm.