In all honesty I'm not sure how giving much longer helps considerably.
I learnt things like that for school with my short term memory on the basis I had to recite it once and that was it. So I'd learn it the night before, recite it perfectly, and have forgotten it two days later.
If I needed to learn it for longer (eg a concert) I could learn it over about 2-4 days much better, in fact I can recite most of those I learnt at primary including ones that are very long.
However I know I find poetry easy to learn, and we had a poem a week to learn and I never had a problem. My db found it a real grind. In fact usually me and my dsis could recite the poem he was learning before he could. But again, if he had 3 weeks, what he'd learnt the first week, he'd forgotten by the end of the second.
Dh says I can find a poem for each occasion. He doesn't say it in an admiring way either 
But with the other homework that sounds ridiculously too much.
To compare in year 3, my dc have typically 8x spellings to learn, and write a sentence for each. 3 times tables or a maths sheet-about 20 questions, reading to a parent. That goes out on a Wednesday, is in the next Tuesday.
Dd2 had to learn a poem (similar length) one week, but that was instead of spellings. She had to copy it out and learn it. That was her literacy homework for the week.
I'd put the fight in that there is too much homework, full stop. Not focus on one particular one.