Spirit stones, pills, elixirs, and many more; are necessary cultivation resources. Environment is also an important thing for cultivator. If they could find an environment where abundant spiritual power exists, they could advance smoothly.
To cultivators, the entire process of entering another stage usually takes 3-5 years or more, depending on the cultivation resources., their environment, and their spiritual root.
Afterwards, cultivators need a place with Spiritual Energy to cultivate in solitude. During this period, it's best to prevent any dramatic shifts in mood because only calmness can make the process of promoting the cultivation level go smoothly.
Most importantly, battles must be avoided, and they must absorb a certain amount of spiritual energy from their surroundings.
Some people might take decades, or even hundreds of years, to reach a higher step if they have a Psuado Spiritual Root (the spiritual root of all elements). People here started to cultivate when they turned six years old.
First, they had to absorb Qi energy from heaven and earth, nourishing and strengthening the bodies. They need to start at stage 1 of Qi Condensation.
The process might take five to ten years or longer. From one stage to another, it took a month or longer to advance to another stage (based on resources). There are twelve stages of Qi Condensation.
After that, they have to spend two to three years and longer to establish their foundations. And the same as Qi Condensation, they need time to advance to another stage. The process is long or short, based on their cultivation resources and their environment.
Once they establish their foundations, their appearances will stay forever at the level at which they establish their foundation. However, if they want to look older and more mature than before, they could continue to grow through some other methods.
For cultivators with Supreme Spiritual Roots (Evolved Element), they became Core Formation masters around the age of 15+ or older. The cultivators who were born with this spiritual root are one in trillions of people. 1/10000000000
To cultivators with Heavenly and Mutated Spritual Roots (One spiritual root), they became Core Formation masters around the age of 30+, 40+ or older. The cultivators who were born with this spiritual root are a hundred in a million people. 10/1000000
To cultivators with True Spritual Roots (two to three elements), they became Core Formation masters around the age of 100+, 200+, 300+ and older. The cultivators who were born with this spiritual root are 400000/1000000.
For cultivators with Psuado Spiritual Roots, it took them decades to become Core Formation masters. The cultivators who were born with this spiritual root are 600000/1000000.
Note: Age here doesn't matter because their lifespans increase as they advance to a higher level. However, if they stuck at their levels for a long period of time and couldn't advance to another level, their lifespan will come to an end and they'll die.