Try to load your final application ( Published application on Qlikview Servewr ) from qvds only, that will reduce reload time.
Avoide Concatenate and joins in this application, if required do this in previous level. That means when you are creating QVDs, do join or concat or use where in this application.
Even a where clause increases load/reload time. However, a time lapse in the previous level or in the last level, the total time taken might get to be more/less the same. How's the difference measured/felt advantageous?