stent safety

i had an angioplasty process done on my father at apollo hospitals new delhi in which he was placed a drug eluting stent by the help of judkins all star guidewire . i am a resident of a very small town and am forced to opt for new delhi for any diagnosis.i want to know that after 20 months of stenting what are the best possible tests or treatments so that we can be on the safer side before any trouble arrives.he is nearly 62 yrs old having an ef of 38 % and nearly no complications.what is the life of a stent ? do we have to change it ?

[Cleveland Clinic]

The stent stays within his heart for his whole life. Drug eluted stents are better at preventing restenosis ( re narrowing)of the lesions than uncoated stents, but they require that plavix be taken for longer periods of time, usually at least 2 years.
He needs to be on a cholesterol lowering medication, beta blcker and ace inhibitor, in addition to aspirin for life and plavix for at least 2 years.