In this paper, a long-term production planning problem is considered with the objective criteria Cmax and Tmax and under resource capacity and precedence constraints. The case study presented is characterized by four years planning horizon, 3552 operations, 51 workers and 57 units of equipment. The solution method elaborated in this study is a heuristic algorithm. Its performances are evaluated in numerical experiments. New procedures for makespan and resource load estimation are developed in order to identify bottleneck resources. The makespan estimation algorithm is tested on the well-known PSPLIB benchmark library where the best known lower bounds are improved for 5 instances. This procedure can also be used for the estimation of the gap from optimal value of the makespan time provided by the heuristic algorithm.