Following is our preferred schedule for acclimatizing on Everest.
Trek to BC 10 days
Arrival BC April 1
Climbing C1 April 7
Back to BC April 8
Climbing C2 April 11
Back to BC April 13
Climbing C2 April 17
Climbing C3 April 19
Back to BC April 20
Trekking down April 21
Back to BC April 26
1st summit attempt May 1-7
Trekking down May 7-12
Back in BC May 13
Last summit attempts May 16-30
This schedule allows plenty of time for upcoming illnesses and rest in the valley whilst climbing slowly. In addition, it provides for 2-3 summit attempts. It requires that you reach BC early and leave late. It also requires the Icefall and other fixed rope preparations to be done in time.
The weather conditions will obviously have the last word on all the dates stated above. The important part is that you are ready for the periods of weather windows that usually occur in beginning and end of May.
If you followed us on the Everest Internet Experiment in the spring of 1999, you might have noticed that we skipped acclimatization at C3.
We had started that procedure 2 years earlier, after noticing that sleep at C3 wore us down rather than acclimatized us further. Instead, we now stay longer at C2 (5-7 days) and climb up to 7000 meters (the beginning of the Lhotse face) several times during the stay. In addition, we usually climb straight from C1 to C2, after spending 2-3 days at C1.
This means that we climb from BC to C1, stay there for 2-3 days, continue to C2 and stay there for another 5-7 days (whilst climbing back and forth the Lhotse wall), then returning to BC for a rest in the valleys.
To us, this approach means more time at altitude above BC, without the constant dangers and wear of climbing up and down. Also, it provides plenty of time to rest at low altitude (5 days including the trek) and to be back in good time for a possible weather window. This acclimatization has left us well adapted to the altitude and strong for the summit attempt.
We don't recommend it to you however, since it requires that you are already familiar with C3 and the route up.
As a first timer, you will benefit greatly from "knowing the route" before your summit attempt. Also, our approach definitely requires that you are well familiar with your own specific reaction to altitude.
You could skip one of the acclimatization steps only if you are seriously running out of time. It's better to have time to trek down the valley for a rest, than to try a summit bid completely wasted. Anatoli Boukreev always stated that a trek down is the most important key to summit Everest. We usually go down to Debouche, the tree line at 3800-meters/ 12500 ft, in order to strengthen our tired bodies with fresh oxygen and refresh our battered minds with some foliage and time out from BC.
You will digest food better, sleep soundly and have some time to think your climb over. Climbing wounds and alpine aches will heal quickly. Only after a few days, you will feel incredibly stronger.
Some climbers don't like to go down because it exposes them to colds and flu viruses carried by trekkers. Our experience is however that it is well worth the risk, due to the significant benefit that the stay on low altitude has on the body.
If you are finished early with your acclimatization, a brief cold shouldn't ruin much anyway. Don't stay down too long however, because you do lose some acclimatization in the process.