Bodhisatta practices in Theravada are mentioned in Buddhavamsa, Jataka and Apadana atthakatha, especially in Visuddhajanavilāsiniyā, Apadana Atthakatha, the commentary of Apadana, which is believed to be a late addition to the Pali Canon, added after the Second and Third Buddhist Councils. This is probably why we hear that the notion of bodhisatta is a late addition. However, in Theravada countries like Sri Lanka where I come from, the bodhisattas are widely accepted. (See also the wikipedia section on Theravada bodhisattas. https://en.wikipedia.org/wiki/Bodhisattva)
According to Buddhavagga section in Apadana Atthakathaa, Theravada Buddhism has ten perfections dasapāramitā (Giving, morality, renunciation, wisdom, energy, patience, truthfulness, determination, loving kindness and equanimity)
and there are three types of bodhisattas, the ones aspiring to be Sammāsambuddha, Pacceka Buddha (a private Buddha) and Savaka Buddha (arahant).
According to the section Buddhavagga in Apadana Atthakathaa, to become a Sammāsambuddha, one requires either 4x10^140 (cattāri asaṅkhyeyyāni), 8x10^140 (aṭṭha asaṅkhyeyyāni) or 16x10^140 (soḷasa asaṅkhyeyyāni) eons of pāramitā perfection
‘‘buddhānaṃ, bhante, patthanā kīva ciraṃ vaṭṭatī’’ti. Buddhānaṃ,
ānanda, heṭṭhimaparicchedena cattāri asaṅkhyeyyāni
kappasatasahassañca, majjhimaparicchedena aṭṭha asaṅkhyeyyāni
kappasatasahassañca, uparimaparicchedena soḷasa asaṅkhyeyyāni
depending on whether he has high wisdom (Paññādhika), faith (Saddhādhika) or effort (Vīriyādhika).
Ete ca bhedā paññādhikasaddhādhikavīriyādhikānaṃ vasena ñātabbā.
Paññādhikānañhi saddhā mandā hoti, paññā tikkhā. Saddhādhikānaṃ paññā
majjhimā hoti, saddhā tikkhā. Vīriyādhikānaṃ saddhā paññā mandā hoti,
A bodhisatta aspiring to be a pacceka buddha requires 2x10^140 (dve asaṅkhyeyyāni) eons of practice.
paccekabuddho paccekabodhisattabhūmiṃ ogāhanto dve asaṅkhyeyyāni
kappasatasahassañca pāramiyo pūretvā
For an arahant a time limit is not given for the bodhisatta period.