It's what ever you are confidant in. I watched TV shows where guys killed Antelope at 60 yrd cleanly....and I just think WOW....I practice out to 40 yrds so that 30 yrd shots are in my mind easier.
Best part is you are confidant at ranges over the normal hunting range of around 30 yrds in most situations...meaning the 60 yrd practice makes the 30 yard kill shot much more confidant.
JMO