Good day guys. I was thinking of getting one of those external portable batteries but wondered if it is worth it for my needs. I would not be charging frequently but once per 2 days at least maybe twice per week as I am not that mobile. I would like to know what is the battery longevity in such portable battery packs since I am hoping one would last me 3 years if it is possible. Since I would use it for my Nexus 4 which has 2100mAh battery, keeping in mind my modest charging needs, should I take 3000mAh or 6000mAh battery pack? If battery packs do not last 3 years then I don't see the reason buying high-capacity product. Let me know your thoughts. Thanks!