New to roll20-questions regarding campaign creation

My friends and I all played AD&D as kids and teens.  30 years later we have started rping again to reconnect and roll20 was a great way to allow that with long distance friends and the Covid thing.  I bought a membership here and started us off with the free Frozen Sick adventure.  I used to love writing my own adventures and plan to do so with the Wildemount world.  My question is kind of a broad one.  If you are planning on running a campaign is it better to create individual adventures and just upload the characters from one to the next?  Looking at the amount of content in a small adventure like Frozen Sick I am wondering how other DMs manage this.  Any other helpful suggestions or hints would be much appreciated.

At the free or plus level, it's pretty much whichever way you want. With Addons and Modules it is now much easier to delete a whole swath of content by deleting their containing folders. This used to be a real pain. So you can wipe away a lot old content. If you want to build an ongoing campaign though, it's probably easier to keep everything in one campaign long term. At the Pro level, it's probably easiest to keep a main campaign and transmogrify in and out maps and monsters as needed. If you use the API, there's a lot more setup. Sorry, that was kind of all-over-the-place advice. :D In general, I'd recommend keeping all the content in an ongoing game unless/until it begins to take too long to load.

With a PLUS or PRO subscription, you can also import the individual characters into your Character Vault and export them into another roll20 campaign 'game'(as long as the same character sheet type is being used).  That would let you build different adventures or modules as separate Roll20 'Games', keeping the resource load smaller than building a long-term adventure into one huge 'game'. If you're building a fairly lean game to begin with (only a handful of maps, keeping it simple, deleting map pages/tokens when you're done with them,  etc) there's not much need to do that, though, and you can just use one single 'game' for everything.

I ran my whole 6-year 13th Age campaign in the same game from 2014 to 2020. I started with a Free account for the first year. Once I had a Pro subscription I did as Keith says, using the Transmogrifier. I started my current 13th Age Glorantha campaign using the Transmogrifier from the beginning. 

Thanks all for your replies.  I think keeping one going will be the simplest.  I am really enjoying the program.  Next is map creation and story line.  I am going to start with a few possible hooks in Palebank village and let that lead the way.  I have end game ideas but I also want to let them sort of lead the direction at the start and then build a story as we go.  Let the adventure begin!