The Bhagavad Gita throws some light on this question
श्री भगवानुवाच
बहूनि मे व्यतीतानि जन्मानि तव चार्जुन।
तान्यहं वेद सर्वाणि न त्वं वेत्थ परन्तप।।4.5।।
Swami Gambhirananda's English translation -
4.5 The Blessed Lord said O Arjuna, many lives of Mine have passed, and so have yours. I know them all, (but) you know not, O scorcher of enemies!
Shankara's Sanskrit commentary and Swami Gambhirananda's English translation -
।।4.5।। बहूनि मे मम व्यतीतानि अतिक्रान्तानि जन्मानि तव च हे अर्जुन। तानि अहं वेद जाने सर्वाणि न त्वं वेत्थ न जानीषे धर्माधर्मादिप्रतिबद्धज्ञानशक्तित्वात्। अहं पुनः नित्यशुद्धबुद्धमुक्तस्वभावत्वात् अनावरणज्ञानशक्तिरिति वेद अहं हे परंतप।।
4.5 O Arjuna, bahuni, many; janmani, lives; me, of Mine; vyatitani, have passed; tava ca, and so have yours. Aham, I; veda know; tani, them; sarvani, all; (but) tvam, you; va vetta, know not, due to your power of understanding being obstructed by righteousness, unrighteousness, etc. However, parantapa, O scorcher of foes; aham, I know, possessing as I do unobstructed power of knowledge, because by nature I am eternal, pure, enlightened and free.
Thus, assuming we are all similar to Arjuna, we do not remember our past lives due to obstruction in our understanding, where as the Lord knows everything as He/She is enlightened and free. The implication is that memories of experiences of past lives are hidden/obscured, rather than completely wiped out.