I have bought Mi power bank which is manufactured 1 year back is it okay

It depends on the quality of your powerbank. 

Like MI 3i power bank which contains  20000 mAH battery may a good choice for you 

It takes 6 hours to charge with 18w fast charger. 

I've purchased it before 1 month 

& now a days  it is giving me a good performance.

It takes full night to charge with USB type charge.😂😂😂