Staircases, mountains, long lonely road ahead are common images for progress. Linear images.
Linear progression along a set sequence in Ashtanga is another example. The quintessential next pose defines advancement.
I wonder if a spiral for the image of progress serves better in Yoga.
One can go further without going farther.
For example, in primary series, how about a considerably smaller subset but drills deeper at each moment? A subset such that it covers all planes of spinal movement.
My favourite is (after the Surya Namaskara opening) Padangusthasana + Trikonasana + Parivrita Trikonasana + Prasarita Padotanasana D + Utkatasana + Janu Sirsasana A + Baddha Konasana + Urdhva Dhanurasana + Pascimattasana + Sirsasana + Balasana + Savasana.
One can drill deeper in many ways. For example, long, thin and subtle breathing with meditation on the “inner touch of breath” in each asana, lasting 10 breaths or 20 breaths or longer. In other words, Pranayama. It could be chanting OM or Gayatri Mantra or any appropriate meter. Or it could be holding out breath (Kumbaka) after each exhalation.