Hellow Mister Hugill! I've had the same question myself when making a series that I'm not sure my viewers are as excited to watch as I'd hoped they'd be. When it comes to figuring out whether or not to keep up with a series, you'll need to go through a few questions for yourself.
1) Am I enjoying making this series?
This is a huge question that can really help any channel, big or small. If you do not enjoy making videos of a certain content, your lack of enthusiasm will likely show on your videos. It's like going into a job you hate everyday: You'll hate every minute you spend in your office, you'll hate everything that is going on, and you only find joy when its all over. The key to having an authentic channel that your subscribers and viewers enjoy is to make sure you are making content that you love and enjoy creating.
You've probably seen/heard that everywhere, but its a tried and true mentality!
2) Is there a way I can spice things up?
Your channel can be kind of like a relationship: after a longer period of time, doing the same thing over and over again tends to wear on the relationship, eventually making one or both of the parties involved feeling disinterested in the partnership. If you DO enjoy making this series but feel like its in a bit of a slump, find a way to spice it up! Add some cool overlays, make a new exciting intro/end card, find some BOMB sounding music to put in the background that gets your and your viewers active and pumped! Maybe even try to do something different for each video, doing that will help you feel out what sticks and what doesn't. Also, by making a bit more variety, your viewers will go into your videos thinking, "I wonder what will be different in this video?!" It keeps your series alive and also gives it a new skip to its step!
3) Ask for suggestions!
Your subscribers are a great source to pitch questions to and will love knowing that their assistance now can/will help out your channel farther on down the road! Your subs want you to succeed, it's just human nature, and if they see you reaching out to them in regards to helping out the channel you are both invested in, they'll be sure to give you honest and thoughtful advice.
I hope something here helped, I have to ask myself these questions everyday to make sure I am staying true to my channels vision and keep at it! Good luck, my good sir!