Pg. 84 of DMG says six to eight medium to hard encounters a day, and list a daily exp budget of 9000 exp per character.
That works out at around 4 medium (4800exp/character) and 2 hard(3800/character), with maybe a quest reward thrown in to push it up to 9000 exp for the day.
The difference between the exp for 10th and 11th level is 2100 exp.
I.E. A 10th level character makes 11th level in 2.3(ish) adventure days.
I have multiplied the amount of exp earned for defeating a monster by 0.4 which means you have to defeat 2.5 times as many creatures to level up. I do give some quest exp
Other house rules:
1. You have to undertake some training to level up at odd levels - this doesn't have to be after getting the exp (ie after becoming level 3 the player knows before they can become level 5 they have to at some stage get some training)
2. Lingering injuries - but I have my own rules on how you get them, what they are and how to remove them.
3. Peak condition benefits - if a PC is rested and has done some training or gained some morale type benefit (ie trained with Master Bob, or listened to a great song) they gain a small edge (one example is "powerful - you may re roll a single damage dice on 3 occasions, another is hardy - you can automatically succeed at a single death save)
4. Limited use items (ie potions, scrolls, some wands) when you use them you roll a d4 on a 1 it's the last use. On any other number there is still some magic left (the players love this, it stresses the unpredictability of magic). Sometimes it's a d6 - if you roll a 1 it drops to a d4 next time (same with d8,d10 etc) (I charge double for PHB healing potions as a result)
Rules 1-3 above and the slow exp is partially to stretch out the time taken in game.