May I use the same data in several time series intervals?
I dont see a problem in „reusing“ observations. Its just new/different info coming in. The question is more if the model will train/perform well with a short lookback or timelag. Why dont use a long(er) sequence of data to predict (eg) the movement in 3h steps. I wonder why you dont use all the data you have to train the LSTM and update the data stepwise. More data usually is better!