Phal: excessive blooms and bloom duration questions

[Nali12]

Some of my orchids have decided to bloom this spring, much to my delight, but one thing keeps worrying me - some of them seem to be set to grow too many flowers, sending multiple flowering spikes that branch off into numerous more spikes and so many flowers that I don't feel like the plant could sustain them all. The orchids seem to agree with me, and sometimes the first, second, or third flower buds seems to wilt and fall off without ever opening. The blooms also don't seem to last long. When I bought my first orchids from the nursery, some of them held their flowers for up to 8 months (it was amazing!). Blooming second and third time in my care now, they don't seem to hold their flowers long, sometimes first flower will wilt and fall off before the rest of them open up (in other words, the flower buds bloom like an estafette one after another).

My questions are:
1) How do I encourage the orchids to bloom with one strong flower spike, instead of spreading their strengths thin growing branched spikes?
2) How do I make the bloom last and hang on there, instead of blooming as a cascade, one bud opening up as the next one is already wilting?

The orchids in the photos are standing next to a window that gets bright scattered light for about 5-6 hours a day. Watered every three to four weeks with a diluted 20-14-13 fertilizer per instructions on the box. The first, larger orchid is trying to grow 40+ flowers. The little orchid w/ white-pink flowers is in process of blooming, but two flowers are already wilting as the rest of the buds haven't yet opened up.