If you're doing video's you might see some series do better then others, or some don't get noticed at all. While still having a VERY small channel, I do recognize a change already with a serie that I have been doing. At what point would you call it and move on to something new? Curious about you guys' answers!
To me you need a goal for the series and if you reach it, end the series there. It could be (if going off Minecraft and that you have a Hardcore series) do Advancements, Get to the End in Hardcore, approach the game a different way that is your own goal, Redstone Builds. Or like I've seen with many: do PVP, Breaking the Game and what results are yielded from it, a Datapack Let's Play and so on with more particular approaches to a series. You need to carve your own niche or have your personality be the reason people watch if the content isn't enough. There is many aspects you can approach for Let's Plays, Analytical and more to make content on.
I'm more into Mods/Datapacks so I just cover whatever content for mods I find interesting from those I've reviewed in the past as my usual uploads and the Let's Plays go deeper into certain ones that I feel make a good series or are mods that I find are the highlights of the version I was playing on. I started my channel with covering Fabric mods as Fabric was a new thing then and I'm also into fewer downloads on older versions/newer content that goes unnoticed so I went with that by review mods first and then moved to Let's Plays among Datapack, Modpack, Resource Pack, Bedrock content and more.
For me as someone that got into Let's Plays a few months ago (and has 3 different modded series, 2 Fabric, 1 Forge) I found that I wanted to go with reasonably sized modpacks (I created myself with mods I'd reviewed in the past, and as I review niche/new mods it made things more interesting so it wasn't just the same content people have seen over and over. Repeating what's trending wasn't interesting to me and didn't seem the way to go (playing mods in modpacks on 1.12.2 with the same mods used over and over). So as I enjoy niche/new mods and found out Fabric as a new niche, it seemed like the right time to make a channel about that).
To me with my 13 episode Let's Plays I played different mods (1 or a few with more content, and a few sprinkled it to showcase smaller stuff that breaks up the larger content mods in certain episodes).
And my larger one was just me learning mods I've never played before on the Mod Dev server for the Fabric Modloader (so a whitelisted private server with the big mod makers for that Modloader and being able to get in as I'm a well known and trusted member of the Fabric community, and many of the Mod Devs know me). In short think ForgeCraft if you've heard of that but for Fabric (ForgeCraft is a Mod Dev Server by the Forge Team and the Major Tech/Magic Mod Devs, those mods end up in 90% of modpacks you see and is why they are part of the popularity listing on Curseforge, so those mods get chosen off on ForgeCraft to show the new cool ones and how server performance is besides upcoming ones for each version). And I did that for 29 episodes until I just got annoyed with the survival situation and episodes were taking too long to get things done and didn't work with too much off camera preparation (mining resources can be boring and a lot of prep with mods isn't always that exciting for viewers or needing to make it sometimes) so I changed to a creating in blocks in creative and looking at what they do approach for 29 to 32.
While you won't come across the same as I will you do need to think about what content you enjoy/think others will want to see. I saw a niche I was into, a particular new thing came out and I focused on that in my own way rather than the tutorials or highlighting channels I've seen, or that Fabric was so new and people didn't see the 'BIG MODS' so I and made my own modpacks to showcase what it does have that is good besides what people think is good. And as someone with experience in about 70+% of the mods created for that modloader I knew which to use and which I was comfortable with besides the ones that were for a surface level audience.
To me Minecraft a big and endless game, so a series can go on to even a thousand episodes. But most Minecraft series Content Creators stop after killing the Ender Dragon, building a lot of building, finishing all achievements and finally making their world available for download. I personally am going to start a Minecraft series in the future and I am not going to end it...
That's all I want to say. Hope you all find it useful !!!