Presidential and parliamentary elections in Liberia on 10 October raise again the matter of presidential term limits.

After a crowded career in commercial and development banking as well as director of the United Nations Development Programme in Africa, President Ellen Johnson-Sirleaf told us that, for her at least, two terms in the presidency was plenty.

Over two decades into what is known as Africa's second liberation – the collapse of most one-party regimes and their replacement by some form of pluralist politics – Johnson-Sirleaf's view is far from universally shared on the continent. Last week, parliamentarians in Kampala clashed after an ugly debate in which some political hacks tried to push through a bill abolishing the age limit of 75 for presidential candidates. Its aim was to clear the way for Ugandan President Yoweri Museveni, in power for 31 years, to stand for yet another term in three years' time. This week grenades were thrown at the houses of two of the MPs who opposed the measure.

In Kinshasa, multiple rebellions, several of them urging Congo-Kinshasa President Joseph Kabila to stand down as the constitution specifies, are gathering force. And in the second-longest presidency on the continent, Zimbabwe's President Robert Mugabe, 93, speaks confidently of winning another term next year. His deputy and putative successor, Emmerson Mnangagwa, claims to have been poisoned by a rival.