Tipitaka memorization is a rule of monks. It isn't just a choice. They must done it.

Translation with description: 

https://unmixedtheravada.blogspot.com/2017/09/how-to-find-right-dhamma-teacher.html
and:
https://unmixedtheravada.blogspot.com/2017/04/guide-to-done-ganthadhura-and.html

From: Vinaya-commentary (link)

Bahu sutamassāti bahussuto. Sutaṃ dhāretīti sutadharo; yadassa taṃ bahu sutaṃ nāma, taṃ na sutamattameva; atha kho naṃ dhāretīti attho. Mañjūsāyaṃ viya ratanaṃ sutaṃ sannicitamasminti sutasannicayo. Etena yaṃ so sutaṃ dhāreti, tassa mañjūsāya gopetvā sannicitaratanasseva cirakālenāpi avināsanaṃ dasseti. Idāni taṃ sutaṃ sarūpato dassento ‘‘ye te dhammā’’tiādimāha, taṃ verañjakaṇḍe vuttanayameva. Idaṃ panettha nigamanaṃ – tathārūpāssa dhammā bahussutā honti, tasmā bahussuto. Dhātā, tasmā sutadharo. Vacasā paricitā manasānupekkhitā, diṭṭhiyā suppaṭividdhā; tasmā sutasannicayo. Tattha vacasā paricitāti vācāya paguṇā katā. Manasānupekkhitāti manasā anupekkhitā, āvajjantassa dīpasahassena obhāsitā viya honti. Diṭṭhiyā suppaṭividdhāti atthato ca kāraṇato ca paññāya suṭṭhu paṭividdhā supaccakkhakatā honti.

Ayaṃ pana bahussuto nāma tividho hoti – nissayamuccanako, parisupaṭṭhāpako, bhikkhunovādakoti. Tattha nissayamuccanakena upasampadāya pañcavassena sabbantimena paricchedena dve mātikā paguṇā vācuggatā kātabbā pakkhadivasesu dhammasāvanatthāya suttantato cattāro bhāṇavārā, sampattānaṃ parikathanatthāya andhakavindamahārāhulovādaambaṭṭhasadiso eko kathāmaggo, saṅghabhattamaṅgalāmaṅgalesu anumodanatthāya tisso anumodanā, uposathapavāraṇādijānanatthaṃ kammākammavinicchayo , samaṇadhammakaraṇatthaṃ samādhivasena vā vipassanāvasena vā arahattapariyosānamekaṃ kammaṭṭhānaṃ, ettakaṃ uggahetabbaṃ. Ettāvatā hi ayaṃ bahussuto hoti cātuddiso, yattha katthaci attano issariyena vasituṃ labhati.

Parisupaṭṭhāpakena upasampadāya dasavassena sabbantimena paricchedena parisaṃ abhivinaye vinetuṃ dve vibhaṅgā paguṇā vācuggatā kātabbā, asakkontena tīhi janehi saddhiṃ parivattanakkhamā kātabbā, kammākammañca khandhakavattañca uggahetabbaṃ. Parisāya pana abhidhamme vinayanatthaṃ sace majjhimabhāṇako hoti mūlapaṇṇāsako uggahetabbo, dīghabhāṇakena mahāvaggo, saṃyuttabhāṇakena heṭṭhimā vā tayo vaggā mahāvaggo vā, aṅguttarabhāṇakena heṭṭhā vā upari vā upaḍḍhanikāyo uggahetabbo, asakkontena tikanipātato paṭṭhāya heṭṭhā uggahetumpi vaṭṭati. Mahāpaccariyaṃ pana ‘‘ekaṃ uggaṇhantena catukkanipātaṃ vā pañcakanipātaṃ vā gahetuṃ vaṭṭatī’’ti vuttaṃ. Jātakabhāṇakena sāṭṭhakathaṃ jātakaṃ uggahetabbaṃ, tato oraṃ na vaṭṭati. Dhammapadampi saha vatthunā uggahetuṃ vaṭṭatīti mahāpaccariyaṃ vuttaṃ. Tato tato samuccayaṃ katvā mūlapaṇṇāsakamattaṃ vaṭṭati, na vaṭṭatīti? ‘‘Na vaṭṭatī’’ti kurundaṭṭhakathāyaṃ paṭikkhittaṃ, itarāsu vicāraṇāyeva natthi. Abhidhamme kiñci uggahetabbanti na vuttaṃ. Yassa pana sāṭṭhakathampi vinayapiṭakaṃ abhidhammapiṭakañca paguṇaṃ, suttante ca vuttappakāro gantho natthi, parisaṃ upaṭṭhāpetuṃ na labhati. Yena pana suttantato vinayato ca vuttappamāṇo gantho uggahito, ayaṃ parisupaṭṭhāpako bahussuto hoti disāpāmokkho yenakāmaṅgamo, parisaṃ upaṭṭhāpetuṃ labhati.

Bhikkhunovādakena pana sāṭṭhakathāni tīṇi piṭakāni uggahetabbāni, asakkontena catūsu nikāyesu ekassa aṭṭhakathā paguṇā kātabbā, ekanikāyena hi sesanikāyesupi pañhaṃ kathetuṃ sakkhissati. Sattasu pakaraṇesu catuppakaraṇassa aṭṭhakathā paguṇā kātabbā, tattha laddhanayena hi sesapakaraṇesu pañhaṃ kathetuṃ sakkhissati. Vinayapiṭakaṃ pana nānatthaṃ nānākāraṇaṃ, tasmā taṃ saddhiṃ aṭṭhakathāya paguṇaṃ kātabbameva. Ettāvatā hi bhikkhunovādako bahussuto nāma hotīti.