As per the Ahnika Granthams, Purusha Suktam must be recited during tiruvaradhana tirumanjanam of household Perumal. If one has time, one can recite tirmanjana kattiyam, Sikshavalli, etc. Purusha Suktam is prime requirement.
If an idol has been consecreated, tiruvaradhanam must be performed. Failing to do so will diminish the presence of divinity in the idol (sAnnidhya). This will lead to an even bigger offence. If the idol has not been consecrated, no harm results if tiruvaradhanam is not performed.
With regards to Shalagrama tiruvaradhanam, it is special. It is beneficial by making small efforts to begin with, like performing tiruvaradhanam on amavasyai, ekadasi, Fridays, etc. This will gradually lead to the practice of regular tiruvaradhanam.
When one is absolutely not in a position to perform tiruvaradhanam, manasiika aradhanam can be performed. But, Tirukkudantai Andavan used to say it is not difficult to perform daily tiruvaradhanam. According to him it is enough if one ceremonially seats Perumal, perform tirumanjanam and offer prasadham and it is not difficult.
Performance of aradhanam that involves physically touching Perumal requires cleanliness to an extent possible. It is better to make space for the clothes to be dried for the next day tiruaradhanam or one can wrap the dhoti in a woolen blanket and use it the next day.
According to Swami Desikan, one should not be lazy on matters related to tiruvaradhanam sandyavandhanam etc.