Brother, do not believe in Suni-Sunai baatein. Just strictly follow the maintenance schedule as per your car's owners / users manual, and take steps accordingly. If it says to change at 40-50K Kms, then you may change them, otherwise, if they are not creating any problem, and schedule says to change them after 60-80K Kms (let's say), then change them after that much interval.
I am of the opinion that if any component is working absolutely fine and not creating any issues, then no need to do any chaaeer-chaar with them.
I know of only 02 reputed brands regarding spark plugs; DENSO and NGK. You can look between any of these two brands and buy the plugs which meet OEM requirements.
I hope, it helps. Thank you.