Some strategies work better in a timeframe which is not provided by default in MT4. And I do have a specific requirement to plot 90 min charts in metatrader which is not available by default in metatrader. Iam using 90 min charts for Ichimoku Shorter term Trading system. Moreover, this method will update your custom chart in real-time, so it really is just as good as the default timeframes of the platform.