My first 3e campagin ran for about 1 year. The characters all started at first level and at the end, when the final climax series of adventures took place to bring the campaign to an orderly end, the characters were all in the 8th-11th range.
Granted, character death was relatively common... raise dead and the like were very, very rare. But in the end, we all had a great time.
Advancement in D&D is like most other things. It is a suggested rate. In my second campaign we fiddled with the advancement by altering the XP chart a bit. In the end, we opted for this:
Alternate XP Awards System
Take the average level of the party (P) and compare this to the highest level member of the party. If the highest level member of the party is four or more levels above the average level, the increase 'P' by 50% of the difference, round up. For example, if the average level of the party is 5 and the highest level member of the party is 11th, this is 6 levels over the average, so increase the value of P by 3 levels, or 8th.
Now, evaluate each opponant within the encounter as follows: Using P - the Challenge Rating of the opponant, compare to the following chart:
(P-CR).......XP Awarded
.8 or more ......... 20
.7 ................. 30
.6 ................. 45
.5 ................. 60
.4 ................. 90
.3 ................ 125
.2 ................ 180
.1 ................ 250
.0 ................ 375
-1 ................ 500
-2 ................ 750
-3 .............. 1,000
-4 .............. 1,500
-5 .............. 2,250
-6 .............. 3,000
-7 .............. 4,500
-8 or less ...... 6,000
So, once you know the XP award for the opponent within the encounter, divide this equally into the party.
So... for example, if we have five characters, average party level is 5th, and the value of P is 5 and these brave souls complete an adventure with several combats resulting in 10 CR1 creatures, 6 CR2 creatures, 4 CR3 creatures, 2 CR4 creatures, and 1 creature of each CR from 5 to 7, then we have:
P(5)-CR(1)=4 = 90 x 10 creatures = 900 XP
P(5)-CR(2)=3 = 125 x 6 creatures = 750 XP
P(5)-CR(3)=2 = 180 x 4 creatures = 720 XP
P(5)-CR(4)=1 = 250 x 2 creatures = 500 XP
P(5)-CR(5)=0 = 375 x 1 creatures = 375 XP
P(5)-CR(6)=-1 = 500 x 1 creature = 500 XP
P(5)-CR(7)=-2 = 750 x 1 creature = 750 XP
900+750+720+500+375+500+750 = 4495
4495 / 5 = 899 XP each.
This system allows for quicker advancement in the earlier levels, quickly tappering off and making the moderate levels last much, much longer.
Consequently, very high powered people feel that way, high powered spells and the like are much delayed, XP costs in magic items feel harsher and thus this reigns in magic and the like.
It worked well for us.
Our sessions when we had our camapigns running were 1 per week, 4-6 hours each. We have two new campaigns starting up in the next three months. One is a Star Wars game, and the other is my next UMBRAGIA campaign -- taking place (starting) on the month prior to the next Age of the Dragon. We plan to use this system for advancement. Should be a good time.