Permissibility of sleeping besides ones infant son

Assalaamu alaikum wa rahmatullah
Respected Mufti
While my husband is at work and my son is napping during the afternoon, i lie down with him instead of placing the child in the cot. This has upset my husband. He wants the child in the cot even if he was not at home. Kindly offer me some Islamic Guidelines on my relationship with my son
a.) Am i allowed to sleep beside the child and until what age will this behaviour be condoned under the Shariah?
Jazakallah khair