You have raised a very important question; it is something every Muslim ought to know as it relates to our eternal life.
The second foremost duty, according to Islam, as reiterated in the Qur'an is to excel in honoring our parents. Allah says,
"Your Lord has ordained that you shall worship none but Him. And do good unto [your] parents. Should one of them, or both, attain to old age in your care, never say "Ugh" to them or scold them, but [always] speak unto them with reverent speech, and spread over them humbly the wings of thy tenderness, and say: "O my Lord! Bestow your grace upon them, even as they cherished and reared me when I was a child!" (Qur'an:17:23)
Explaining this, the Prophet (peace be upon him) said, "woe to him who failed to enter paradise by failing to take care of his elderly parents!"
So, it is one's responsibility to take care of his parents in old age; it is not a simple recommendation but a duty incumbent on him or her; by neglecting this important duty, they are incurring the wrath of Allah. The Prophet (peace be upon him) said, "Shall I tell you three of the most grievous sins? He repeated the question three times, whence the Companions said, "Of course, O Messenger of Allah," then he said, "To associate parents with Allah, to displease one's parents, and to bear false testimony." (Reported by Bukhari on the authority of Abu Bakrah Nufay b. al-Harith)
It is ironic to see that parents go out of their way to sacrifice all of their comforts in taking care of their children, while children neglect to take care of their parents. How often do we see children who send away their parents to spend their last years in a nursing home, all alone; which parents would even contemplate sending their children-who need desperate care- such a facility? This is why Allah orders us to treat our parents most honorably when they attain old age and take care of them, and never speaking an unkind word to them, even though their behavior is irritating because of the hormone changes in their bodies due to old age. Didn't they tolerate with great patience all of our follies and tantrums, and showered us with tender care and mercy?
May Allah forgive us all of our failings, and may He honor us all to fulfill our obligations towards our parents and pray to Allah to shower them with His mercy even as they showered us with mercy when we were little.