'tends to prolong' is correct and usable in written English.
You can use it to describe something that makes a situation longer or lasts longer than expected. For example, "The contract negotiations tend to prolong the usual completion time for this project."
The Chinese focus on building relationships rather than on contracts tends to prolong the negotiation process.
It thus tends to prolong the duration and increase the severity of wars.
Leaning on numbing behaviors (drinking, going home, spending hours on Facebook, eating junk food) tends to prolong both the transition and the difficult emotions.
It is fractured among many groups, another factor that tends to prolong civil wars and make them less likely to end peacefully.
Though the Press's editors have been successful in locating subsidies to make feasible publication of particular projects with extraordinary financial requirements, this process tends to prolong uncertainty over publication and invariably deflects our editors from their true role seeking manuscripts rather than money.
This in turn tends to prolong both the boom and bust stages of the cycle and increase macroeconomic instability.
Indeed, it could tend to prolong the active life of older laptops by making better use of their processor and memory chips.
The history of other democracies' flirtations with martial law contains two lessons: First, even allegedly "limited" emergency powers tend to prolong themselves.
The origins of the campaign are almost entirely emotional and we feel that any attempt on our part to weigh in on the argument will tend to prolong it and make matters worse".
Investigations indicate that dental extractions tend to prolong treatment time, in general [30],[30].
Bertrand Russell, in his behaviorist-influenced 1921, also accomodates inactive pleasure by analyzing pleasure relationally and negatively, as the property of mental occurrences consisting in their stimulating no reflex or voluntary movements that do not tend to prolong the stimulating occurrences themselves (1921, pp. 71-72).
