Lord Shiva is considered as the fire of penance, blazing all over him & from him - a bhakta always try to please his Third eye and get blessings. He is also called Abhisheka Priya. Bathing divine elements is called Abhisheka in sanskrit. The more you bathe him, the more beloved we became. In many temples, a brass or copper pot is hung right above the linga with a small hole in its apex pointing downwards and water keeps dripping on the linga.
Lingam Pooja Daily in temples does abhishekas (Divine Bathing) with fresh milk, Fresh Curd, aromatic herbal powders & water chanting mantra. The common procedure is to use eleven dravyya to the Elevan Rudra Devatas. The number of time done does not matter. What is absolutely required is sincerity of purpose, unflinching devotion, and complete dedication.
Out of all the materials used for abhisheka, the water from the kalasa is most important and used last. 1, 3, 5 7 or 11 kalasas can be set up for abhisheka. Veda mantras are used to purify and sanctify the water Apo Va Idaghum Sarvam - water is the cause for emergence and sustenance of all life. Water as it is has no shape but take the shape of the container in which it is taken. The Brahman cannot be described with specific form or shape. However, the Brahman can be visualized in our mind with specific attributes - Saguna Brahman - the Devatas. This is one reason that yogis prefer 'Manasa pooja'- visualization of the Brahman in the mind and deep meditation, which ordinary persons cannot accomplish.
The Bhagavad-Gita reverberates this over and over.
Some offer worldly goods, others offer sense restraint. Others submit their sufferings or take vows. Many offer knowledge by studying the scriptures while a few make offerings of meditation. Many worship by controlling their senses while others restraint their breath. All these, understand the meaning of service and will be cleansed of their impurities. --- The Bhagavad-Gita 4: 28-30
How many times you do is not important. What we need is sincerity and dedication. The remaining water or the water collected after the abhishek is usually poured to wells or trees. This is just it is a way to show devotion as shiva symbolise the life (supreme soul). So the water left is poured in tulsi preferably or in trees as they are considered satvik tatva.