Typically you should burn your candle 3-4 hours at a time. The candles burn expectancy is 60 hours.
Yes, trimming the wick 1/4 inch will elongate the candles burn expectancy.
When cutting the wick, if it’s not cut properly, you will find the wick be drowned in wax. To Alleviate that problem try pouring out the excess wax to expose the drowned wick and relight.