Loss of campaign momentum is a perennial problem. It is typically the result of one or more of the group losing interest in, and energy for, that campaign. If it's a player, they start becoming harder and harder to schedule in, they stop paying attention in session, and they generally start to make the whole experience feel like a drag. If it's the GM (and it often is!) they find it harder and harder to motivate themselves to prep and to book the sessions. This invariably gets transmitted to the players, who can tell the GM's heart isn't in it. The result is a zombie campaign that nobody is enjoying. To mix my metaphors, such campaigns often suffer death by asphyxiation – without the oxygen of the group's interest they just wither, and one day nobody books the next session.
The Stew article presents some great ideas for avoiding momentum loss during a hiatus, chiefly to do with stirring the pot during the break and avoiding shiny distractions that divert you from the campaign. But to some extent this relies on the group still having momentum; nobody will be bothered to take part in between-sessions activity if they aren't feeling the love.
For me, the way you avoid losing the big Mo is by keeping the campaign within defined boundaries. Nothing can go on forever; we see this in all walks of life, not just gaming. How many times has a TV series overstayed its welcome by one or two seasons, leaving the whole thing feeling tarnished? Well, unlike the TV networks we aren't in this to make money so there's no point in keeping going past the point that we're having fun.
So here's my suggestion. Plan your campaign in self-contained chunks. 8 weeks seems to be a good number, but YMMV. Choose a period of time where everyone can largely commit to attending sessions, and in which a decent arc of the campaign can be played through. (You may find that things don't quite go as you expected, and you need a session or two more – that's fine! Better to exceed your budget slightly than to not have one at all.) Now everyone knows there's a defined end-point, and everyone is working to reach a satisfactory conclusion in that time-frame. You'll be more disciplined about your play, focusing on the stuff that really gets you going.
When you get to the end of a campaign chunk, you can pause for reflection. How are we all feeling about the campaign? Is there something else we'd rather be playing right now? Are we keen to continue, and if so what do we want to do in the next chunk? Is there anything we could change to keep the campaign fresh? My group has developed a tradition of going out for dinner once in a while for campaign reflection, and this would be a lovely way to mark the end of each campaign chunk.
Moreover, the end of a chunk gives you the chance to manage transitions and endings more effectively. Does anyone need to step out of the campaign for a bit – maybe someone has had a baby or is going through a busy patch at work? If so, this change will be less likely to break your momentum. Are people looking to try something different? Because you've built in a break-point, you're managing the tendency for campaigns to peter out, and if/when the campaign finally does end it's more likely to be a nice, satisfying ending that avoids a zombie campaign or death by asphyxiation.