Sporadic use, as opposed to occasional use would be a more appropriate description, a week here and there, and the occasional weekend.
My previous secondary sim was a Vodafone PAYG sim, typically i would need to top it up at least twice on the week+ trips ( out of signal), buying two £10 Big Value Bundles ( 2GB data/ultd text/250mins)
Switching to Giff Gaff and using the goody bag option would appear to make a saving, the only thing i would loose is getting Vodafone Rewards points for which i would have to spend a large sum to get a paltry offer of a smidgen of data, a handful of texts or a crap accessory.
My Main Sim is a Three sim only plan ( grandfathered no longer available) £17 a month for all you can eat everything ( ayce calls/text/data/tethering) if they kick me off that ( as they did with users on the similar oneplan ) and Giff Gaff performs OK, then it will be an option as the main sim, the only downside to Three is there are a few zero signal areas, and a few where i can get Threes VOIP signal, but they wont let me use it, even though my device supports it, as I dont have a phone from Three.
I aim to be using the GG sim in a dual sim Oneplus 6T