They should last longer than a few days. I suspect the plant has been set back between the time the buds set and now. This could happen if the plant was budded in a commercial greenhouse, then shipped to a retail outlet, sat for a while and then moved again to a home, all the while, getting briefly hit with winter outside temperatures. But, the final blow may come if the plant is not in good light in a sufficiently warm room. Plants need good light to maintain the flowers as they grow up and open--a bright windowsill. Plants cannot be allowed to dry out when in flower, and plants use more water when in bloom. Lightly and briefly drying is OK but beyond that point it can be a problem, depending on how far beyond that point. Lipstick type aeschynanthus also are from warm tropical origins (Java) so cannot endure a cold room that is allowed to drop into the 50's (F) at night. The only thing I can think of to suggest, not knowing your plant or conditions, is to grow it in a warm part of the house in bright light, and keep the soil evenly but lightly moist, cross your fingers and hope for the best.

Jon

thanks,one more:
i've discovered something sticky on the leaves of my lipstic plant. not all
of them are sticky,but a few. why!?
nothing else discovered..!?

Stickiness is often a sign of scale. The bugs will suck the sap of the plant and then exude sap from their "other end", which ends up on the leaves. Ants are usually involved--they farm the scale.

But, since you said you didn't find any bugs, I suggest that first you look again really closely to see if there are any tell-tale pale brown dots on the stems that rub off easily (baby scale).

Assuming that you are correct that there are NO bugs, then the next thought is that the flowers are exuding nectar (this is what I really suspect is going on) somehow--perhaps from the cup-like calyxes. I think, I've seen this before on my aeschynanthus. I would just give the plant a shower to wash it off. The sticky stuff could bring on a mold which would leaves black stains on the leaves, which might not wash off. Also, the stuff could attract ants.

Jon