A farming cycle tick happens every 500 game ticks (approximately 5 minutes), which is when crops are updated with their new stats. However, these ticks don't occur if you have an interface open (for example, the Remote Farming window or a bank window) and are delayed until the interface is closed. Thus, Remote Farm won't give live information even if crops update, so there is no point in leaving the window open to watch your crops. However, you can update the information if a farming tick occurs by closing the interface and casting the spell again.