A problem of pace

Adventures designed to last four hours, but really last six.
Dungeons so large that it takes five hours of real time just to schlep between the interesting bits.
Boss fights that drag on for 90 minutes.
The biggest problem I encountered early on when playing with family was the pacing of the Dnd RPG. As I mentioned in a previous post, most people are used to playing board games which run half hour to an hour in length.
Unless your an aficionado, even a three-hour session of Monopoly would feel like a marathon.

Dnd takes a while to set up, a while to get going, and there's an expectation of some sort of satisfactory climax to the story. But it felt impossible to cram that into, say, two hours.
This was especially a problem with fourth edition, where even a simple fight would likely run to an hour. Fifth edition promised you could play in an hour (I remember Mike Mearls talking about this during play testing). But it's not really the case. You can run an encounter in an hour, but not really a proper adventure.

Beating the clock is more difficult than beating any dragon

When I designed what I thought were "short" adventures with four encounters, these ran far too long and in general we were only half way through at the end of three hours' play.
I compared this to the experience you'd get spending the same amount of time watching an action movie or even playing a video game.
It didn't compare.
A fight in an action movie might last five minutes tops. A big climatic battle? Twenty minutes.
The number of beats you're hitting in terms of fights, character interaction and exploration of fantastic locations just did not measure up.
Here's some of the things I started doing to tackle that problem. I did them piecemeal, and some of them seem simple in retrospect, but they added up and now I'm well able to squeeze a decent adventure into two hours.


Dump Healing Surges (or whatever they're called these days): They effectively just give your players more hit points. This makes them harder to threaten, diluting the tension of the game. It means you have to either throw a lot more enemies or a lot more encounters at the PCs. Either way, it drags things out. If your PCs know they have just their starting hit points, plus whatever spells or potions they have to hand, it tightens things up considerably.

Three encounters max. Your party are only going to have time to deal with three proper encounters. Choose your best three, make them flow together and dump the rest. Have one or two others on standby in case the session progresses quicker than expected, or the PCs use a powerful spell to blast through a fight you thought would last half hour, or whatever. It's nice to give PCs a choice of which encounters they tackle, so I use flow charts or mind maps, but I don't let it be possible to meander through five encounters before they reach the finale. THREE encounters, folks!!

Run a timer. Stick an alarm on your phone and set yourself goals to hit before those alarms go off. Maybe you need the PCs to blast through the first fight before the half hour mark. If the alarm goes off and the dice are still rolling, you need to wrap up that battle.
Perhaps you can integrate this into the game. Imagine the PCs are exploring a haunted house - when the clock strikes midnight (an alarm I use myself on the phone) then something happens to move on the scenario: a secret door opens, or monsters attack, or perhaps the spirits that had been harassing them fade away.

Play against the clock. Similar to the above, but actually limit the number of turns the PCs have. In a recent game based on the Labyrinth movie I gave the PCs 13 turns to escape the labyrinth and defeat the Goblin King. It was great fun and everyone appreciated knowing how much time we had left! It added tension and it was also reassuring to the players to know they wouldn't be stuck at the table all night in real life.

Yes, this dude. Again.

Tweak the monsters. Veteran players love working out how to hit monsters. How to target their weaknesses and which spells to pick to capitalise on those with high AC but low WIS, or whatever. More casual players just enjoy hitting monsters. So I lower their AC to ensure they can hit AT LEAST two thirds of the time. It only takes dropping the AC by one or two digits.
I also drop hit points for some boss monsters, to stop the entire fight becoming a grind. But I use the trick of upping damage in order to keep the fight threatening. I don't quite use the old 4e trick of DOUBLING damage to speed up fights, but I might move up to the next dice or add a few more points of damage. It's enough in fifth edition, particularly when there is limited healing.
A feeling of fear and danger is essential, otherwise there's no point having the fight. But make your players feel powerful and satisfied by allowing them to hit the red dragon. Then make them terrified when it deals so much damage with one claw attack.

Because this is what it's supposed to be all about, right?