When less Āsana time than you would like,
better to reduce the number of Āsana,
or the number of repetitions,
or the length of the stays,
rather than, reducing the length of the breath.
Or….. even considering lengthening the breath,
thus even fewer Āsana, all with a longer breath than usual.
Here the Bhāvana could be to observe the effect
of a more spacious than usual Āsana breathing
on a more cramped than usual daily mindset.
The longer term measure of our Prāṇāyāma potential is determined by
our skilful efforts with all four components of the breath in Āsana.
For example can we maintain 188.8.131.52. in Parśva Uttānāsana or 184.108.40.206 in Mahāmudrā?
These days though, it seems that there is not much place for or interest in the use of Kumbhaka
and breathing practices, if used at all it appears to be mainly Cikitsā or about recovery,
or at best Rakṣaṇa or constitutional, rather than Śikṣaṇa and developmental.