Does commercial booze keep fizz better?

[Curmudgeon]

When you mix your own booze together with a mixer, does it stay fizzy as well as commercial stuff, or does it go flat quicker? If so, why?

[Easydrinker]

I blame any lack of fizz upon my buying mixer in litre bottles.
I don't drink a lot of commercial spirit these days, so cannot honestly compare.

Robert.

[Curmudgeon]

Interesting point.

I only ask because on the odd night out I think a mixed drink stays fizzy longer.

The gin and tonic guys will know.

[Mash]

Certainly something to watch. I have started buying tonic in smaller bottles for this reason.

[gaza the instructor]

+1 Mash I rarely drink G'n'T as you know!!
It's the freshness and quality of the Tonic I think.
Also ratio of Gin to Tonic!!