For me personally, in all honesty, I feel that it is a simple choice. I could either commit to Slimming World, and embrace the necessary changes (and they
ARE necessary changes as I wouldn't be overweight if what I was doing/eating was healthy) or continue kidding myself I could muddle through.
I chose SW, and (again, for me) I feel it is not a plan that restricts unnecesarily, nor deprives. I can't imagine being bored as it is not a diet as such, it really is a new way of eating (and drinking lol).
As others have said, there are so many ways you can incorporate what you love into SW - if its a pint or 2 then go for it! You just can't do it every day and you need to flexi-syn it where necessary.
If it simply doesn't appeal to you, and you are bored and de-motivated, then nothing anyone else says to you will matter.
The bottom line is to lose weight, we need to change our lifestyles.
Only you can make that decision to change and follow through.
To directly answer your question - I honestly don't think you can do SW one day, then not the next and so on. Sorry to be blunt, but I'd say that you are only going to struggle that way.
Good luck with whatever you decide, and know that the support is here for you as you need it.
Take care

xx