Can be done but I don’t see any added advantage as 45 AH seems good enough. First see, if your alternator is in good condition or not. Then try to find out why your battery failed, was it over charging or under charging. Connect AMP-Meter on battery terminals and measure the AMPs being provided to the battery. If its higher than 6 AMPS then 70 AH battery will do a fine job. Lest would not die so quickly.
Battery only helps starting your vehicle, running electric equipments once engine is off. As soon as alternator kicks in, it takes care of running all electrical appliances and charging the battery.
I have seen cars, where alternator charges the battery at more than 6-7 amperes as in my old Liana, battery would get fried very quickly and in that case replacing it 60AH or 70 AH would had done perfectly fine.
In case, where charging rate is around 2-3 Amperes then replacing it with 70 AH is asking for trouble.
Important thing is check if your alternator is fine or not.
