Yes. My niramisa sukha has built up over the years.
– It is not anything deep or mysterious.
Amisa sukha, the opposite of niramisa sukha, is the “happiness” one feels when engaged in sensory pleasures. For example, eating a delicious meal, the joyous feeling when buying a new house, or getting a promotion at work.
Those “pleasures” are temporary. Furthermore, they lead directly or indirectly to suffering ranging from just discomfort to real suffering.
On the other hand, niramisa sukha is the relief one gets when one starts seeing those bad consequences of amisa sukha.
– Fewer burdens lead to less agitation of the mind.
– Less agitation of the mind means easier to grasp deeper Dhamma, which in turn leads to less mental agitation.
So, it is a positive loop that leads to accelerated progress.